FunnyBunny

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I need it on curves too!
In Coreldraw you can go in properties and select the curve and it will be there, also if the curve is a curve and not just straight line. Perfect if you want to measure, let's say, the neckline or the armscye. In real life you would run the length with a flexible ruler.
 

It is the thinnest line produced on the device it is presented on. Simple as that.
One pixel on monitors, single cut line on cutting machine, smallest unit on other devices.

No, @Eksdad, you are using the term correctly.  "Hairline" is a device dependent width.  To "do the math yourself" as @loukashsuggests is completely contrary to the concept and utility of hairline widths.  The Affinity suite should support hairline widths.

I have yet to use AD a lot, so I am not sure how it works there. In CorelDraw it is not working any good so what I do there is use its Powerclip feature to fill the content with manually tiled objects of size. I do that rather than do pattern, and then pattern fill because of the poor adjustability of the latter that I simply do the powerclip route as it takes same/similar effort and at least let me adjust the content.
Powerclip is when you turn one object into a container of kind, and the content can be wider than the object but the excess isn't shown.
It isn't a replacement to a well made vector fill of course.

If the delay is because they want to put in a good work with dynamic editing and whatnot it is better than them releasing a simple hack job like CorelDraw non-dynamic stuff.
 
(with dynamic I mean ability to edit/recolor the content.. In CDR you are stilll, in 2021, unable to do it. haha)

I purchased Designer and Photo years ago but I just couldn't replace Illustrator & Photoshop because of a few missing features that are just workflow basics. I've moved to the Windows platform and just downloaded new trial versions of them to give them another chance, and these problems persist. Most of them relate to features that prevent the user from making critical, unprofessional mistakes like inconsistent color use across multiple documents. If you are deigning a flyer, a business card and a name badge, you can't have variations between them. These are a few [very] minor omissions that I am missing that risks me making amateurish mistakes:
- Global swatches don't carry to another document when copy-n-pasting a logo from one document to another (same as in Publisher)
- Swatches not carrying over to the new document also means that overprint setting are lost because overprint is defined in the swatch, not in the object.
- I can't tell what color mode I'm working in. If my mode is RGB for a flyer, I need something to shout out at me, or at least give me a clue that my print job is going to be disaster. A simple RGB/CMYK icon would suffice. Even Photo displays its color mode in the document's header, but Designer [where it's more important] doesn't.
- The colour picker only picks up RGB/CMYK values, not a global swatch. Even if I've pasted a logo into a new document and it's displaying a global color, the eyedropper doesn't read it as a global color so I can't even reliably copy colors from my source logo. 
- To duplicate an object by dragging it, I have to press the Alt key before I select the object, not during the drag. Most of the time, I need to be certain I have selected the correct object before I duplicate it, however, now I have to duplicate something and then find out if I selected correctly. I don't know how many times I have moved items I want to duplicate and duplicated items I didn't want to duplicate because of this. An application is not fast to work in if I'm constantly undoing my actions.
- Changing the colors of margins & guides. If I design a blue brochure, my margins and guides disappear. I need to make them red or yellow or anything. I don't expect to be able to mix my own colors, but a dozen pre-mixed swatches to choose from would solve this problem. (apart from working in wireframe mode)
- Connecting the selected transform corner in the transform palette to the free transform with the move tool. It's very strange that I can select a corner in the transform palette, but then I always rotate around the center. I have to manually type rotation values in degrees to get the rotation around a corner. Why the disconnect? This disconnect is similar to the disconnect I experience between the swatches, color mixer and eye dropper.
- Previewing at export. Even in Photo, I can't see the effect of the level of JPEG compression being applied to my exported files (neither in Designer nor Photo). I have to export a file half a dozen times until I hit upon that sweet spot of small file size to barely noticable quality loss. Even the open source GIMP does this with a live preview at export. I can do awesome professional work, and then break it all with a poor export... and not even realise it.
- Proofing colors. I really need to be able to see how my colors will separate before I save my PDF. If I've accidentally worked in RGB, this will reveal my mistake as I go to repro. Overprinting and knockout will also be a disaster if not picked up in time. (Who here hasn't experienced the dreaded white text set to overprint and wondered where all your text went?). This feature alone forces me to keep a professional, licensed copy of Adobe Acrobat around to preview color separations. In my final repro file, I have to know if my spot colors are still spots and if I'm printing fine black text as 100% black, or a full color breakdown that will turn my single color print job into a full color one. Previewing the separations (or channels in your photo editor) points out my potential errors.
- Overprinting settings. The previous point leads straight into this one. Why is over printing set in the swatch and not the object? If I want some small paragraph text to over print, but large display text to knockout, I have to make 2 identical black swatches to do this. Why can't I specify this on an object-by-object basis? I guess "Multiply" does the same thing and works as a work-around, but you're targeting print designers, and use the term overprint yourselves so why the strange and risky implementation.
- Snapping to "round" values. When manually selecting a color in CMYK, we are inevitably creating a color using round number values from a color chart. It's slow and frustrating trying to select exactly 50% in a slider as it hops from 49 to 51 and back again while we search for that perfect pixel placement. How about snapping to increments of 5% by holding down the shift key? Your snapping features are awesomely powerful, but only in the document. Why not extend this into the sliders and the rest of the application? (Admittedly, I don't know any other application that does this, but it makes sense and would be welcome.)
 
Basic features that are even in open source software seem to be missing. We waited for years to get arrow heads. You claimed it was because you wanted to get it awesome, but they are no more powerful/different to anything else out there on the market. I suspect we only got them when Publisher was released. Did we have to wait for a whole new app to be leased to get arrow heads? Now we sit with other missing basic, common features like:
- Blend/Interpolate
- Stroke drawing tools like a grid tool and a straight line tool. These are enormous time savers.
- Tabs. (I understand you want to protect Publisher by keeping high end text features like hyphenation, drop-caps and text wrap out of Designer, but this feels like a very basic feature compared to your range of kerning, alignment and Opentype features already here from day one)
 
I understand that everyone's needs are different and you can't satisfy everyone, but you are targeting print designers as well and illustrators and web designers, and  these are all features every professional expects and is surprising that they're not here. You give us features that most professionals just leave on the defaults because few of us even understand them (like color profiles and LUTs), but then drop the ball by not pasting a global swatch from one document to another.
It's confusing and just doesn't make me feel confident in the files I send to print.
Please can you look at these issues before adding new features. I understand that new features are needed to sell products, but a lot of us early adopters are just wondering where the small tweaks and refinements are.
It seems that your development team needs to consult with an old school designer or printer to get these fundamentals right. It feels like you've only got young designers who have grown up with an RGB workflow and have never had to bang out 6 flyers in an afternoon and send them to print with the job being rejected.
 
 

Sadly the contour tool is no solution, because it can't generate multiple contours for a shape. Moreover your original shape isn't visible anymore. But in my case I need an original shape combined with three additional contours, that are "live" connected to the shape. As written you can do this with path effects in Illustrator. In Affinity I would need three copies of my original shape, each with a different contour (by contour tool), but all shapes (i.e. objects) in sync, so that changing one copy changes all at once. I don't see a way to do this in AD.
The Appearance panel is more useful than the contour tool in this case. But to get four separate vector shapes out of one object with four contours (=outlines) is a lot of hand work to do. I could explain it in detail, but I fear to would go to far.
Slices are neat to export parts of a design automatically. But there's no way to export the same area twice or more often with different layer visibility for each export. Say you have an icon on layer X and two backgroud designs on the layers Y and Z. In AD you can't place two slices at the same area and then select to export Layer X and Y for slice 1 and Layer X and Z for slice 2. At least I didn't get AD to work this way.
The greatest problem in comparisson to PS and AI are the missing actions. This means that you can automate any workflow in your programm. PS even automates your clicks on the canvas. Yes, AP has makros, but you can automate only a tiny part of all things you can do in AP. For example to copy and paste a image part isn't recorded, you can't record selecting the layers transparency, you can't record selecting a channel, you can't rearrange the steps you recorded, you can't replace steps by a new recorded step... (I stop here).

It's quite useless to discuss the term "professional" this way, since everybody who earns money from Affintiy softwares claims the software to be professional. This way "professional" means everything and nothing.
Whether you regard a software as "professional" or not depends on your needs. Someone who makes illustrations and has plenty of time may be even happy with Mac Paint or something like this and call it "professional". (In fact there's an artist who made some nice images with Mac Paint lately.)
But if you are in a business where you work for clients you need to be fast (even faster), flexible (clients will switch their minds) , relieable (f.e. colours and dimensions must always fit), able to produce the same quality in larger numbers (pages, packages, cards...) and - well, yes - you should be creative, too.
That boils the requirements for the software down to the question: can it handle large numbers of designs fast, variable and always with a predictable and reliable end result. Some softwares fit better here, some worse.
To make it a little more descriptive: I myself work as an illustrator for non-fiction books for children, puzzles and family (board)games. Games often have many cards for example, with icons, text, illustrations and decorative graphics. Even when there's a good briefing, the overall design of the cards changes many times until it's finished. Colours change, icons change, places and sizes of objects change and sometimes it's not clear whether the red or the blue design will be taken in the end. So the same elements must be combined with the red and with the blue design. When icons or illustrations change, they must be replaced in both variations and all - let's say - 45 cards must be exportet as JPEGs or as PDF again, to be shown to the publisher.
Photoshop for example can handle this taks quite easy with stacked layers, smart-objects, layer compositions, actions (and /or scripting) and batch-tasking. Affinity Software makes this a hand-job - each time (switching layer visibility, exporting each card by hand). With Affintiy Software this task is much more error-prone, because eventually you forgot to switch layer X on and layer Y off for this special card.
Well, you could use artboards and symbols extensively, but this makes the creative process much more complicated (should this layer be part of symbol X or symbol Y). I tried it, and it's not nearly as flexible as layer compositions.
Other example: For a childrens activity book I had to create a sheet with stickers that could be pasted into pictures in the book. Each sticker gets 4 contours around the figure:  the main conture defines the punch line, the second is an inner margin to avoid cutting of pieces of the figure, the third an outer padding to mark a safety distance between stickers und the forth a bleed for the background behind the figure. Of course the placement on the sheet must be flexible until the design ist final.
No problem in Illustrator at all: I place the animal images, create vector shapes that form the punch contour and assign 4 contours to each shape. Three of them get a offset-Path-effect for the respective distance. While these are path effects, all contours are updated automatically with every change of the original vector shape. When the design is ready it's exported to Photoshop where I use the selected paths as masks combined with custom actions to export each sticker as croped image in it's own image file.
I found no easy way to do this job in Affintiy softwares. The lack of real actions and scripting is the greatest problem here. Another problem is the missing ability to assign mutliple contours with individual distances to a shape. You can use multiple outlines with different stroke widths, but you don't get shapes with four diffenent offsets in the end. All in all this job becomes a lot of handwork in Affintiy softwares.
These are just two concrete examples. There would be more.
So, call your software "professional" because you earn money from it, if you want to. The problems with minor flexibility, missing functions, some complicate workflows with too many steps needed, missing automation/scripting of ALL functions of the software stay and make the difference to the "industrial standard" softwares.