Amy Choue

No, Font Manager just lets you assign a "temporary" font to replace the missing one, so you can print or export your document. You will still get the preflight error warning you that the original font is unavailable on your system.
Yes, you use the Find & Replace dialog
 Use the Cog menu and under Fonts change the ALL dropdown to Missing
Then in the Font Family dropdown you can select the missing font
Click OK in that dialog to close it and then click Find in the Find & Replace panel
You will then get a list of all the occurrences that missing font is located in your Document. Clicking any of those occurrences will take you to the page where that font is used
You can then change it manually or if you prefer you can use the same Find & Replace panel to assign a new font to replace the missing one for all occurrences where that missing font is found
Either way, this change is permanent and preflight will no longer give an error for that missing font

I came upon this while searching for ways to create epub, and when Affinity Publisher will have epub export. I have used MS word for this, which seems to work fine with text-heavy books and if the book is released only at KDP. But even with an extremely limited experience in all tech-related things, I seem to see coarseness and waywardness in epubs based on Word.  
When will Affinity have epub reflowable option? What great news the release of that would be to those waiting for it, who search for it to find out the state of things as regards to it. Please release it in the near future! 

I came upon this while searching for ways to create epub, and when Affinity Publisher will have epub export. I have used MS word for this, which seems to work fine with text-heavy books and if the book is released only at KDP. But even with an extremely limited experience in all tech-related things, I seem to see coarseness and waywardness in epubs based on Word.  
When will Affinity have epub reflowable option? What great news the release of that would be to those waiting for it, who search for it to find out the state of things as regards to it. Please release it in the near future! 

Hi Amy Choue,
Double check the linked status of your file in your Resource Manager,  additionally, check and tweak the advanced section of the PDF output settings.
You will see options for down sampling images and Allow Jpeg compression (with a quality slider).  Both of which can contribute to this banding effect.
Lee

Amid different things, it can be done this way, as long as it is not too noticeable.  (And if so, I also doubt it will be sufficient to gain a line (except for a last short one).
In my humble view, I tconsider in general that the Minimum word spacing should never be inferior to the width of the letter i, Normal word spacing somewhere round the width of a dot, and Maximum possibly even like an n but should never be greater than the space between the x-height and the baseline of the line above.

The percent values to achieve that can vary following the font chosen. 

Are you sure that you achieved 1-2 fewer lines just by reducing word spacing? To me it appears quite unlikely if you see what happens with 0%. (in APub V1)

Yes, you can go back. But as I explained in the word spacing thread, there were no changes in word spacing so I don't think it will address your issue. And any documents you saved in 2.3 cannot be opened in a previous version.
Windows:

Publisher: https://store.serif.com/update/windows/publisher/2/ Designer: https://store.serif.com/update/windows/designer/2/ Photo: https://store.serif.com/update/windows/photo/2/ macOS:
Publisher: https://store.serif.com/update/macos/publisher/2/ Designer: https://store.serif.com/update/macos/designer/2/ Photo: https://store.serif.com/update/macos/photo/2/

It's possible to reinstall an older version from Serif's site but you won't be able to open documents you saved from 2.3 in that version. And there really is no difference in spacing - if there were, everybody would be screaming because documents saved from 2.2 would be spaced differently when opened in 2.3.
Perhaps you're also thinking of tracking and not just word spacing - designers often tweak tracking just a tiny bit to avoid widows and orphans.
Here are two articles on manually fixing widows and orphans in other apps but of course you'd have to "translate" the features to the equivalents in Affinity.
https://creativepro.com/how-solve-typographic-widows-and-orphans/
https://creativepro.com/the-digital-dish-kill-the-widows-and-orphans/

I don't know what to tell you, nothing has changed with regard to word or character spacing. It might just be that some of your current document's words can't be hyphenated - for example, Girondists won't hyphenate.
If you're using footnotes you can experience big gaps at the bottom of a column if there isn't space for the entire footnote below the footnote marker as shown in the screenshot below. In this example there are no flow options set for the body text or footnote text. To fix this, I could enable "split notes" and the note will be split across the columns. No amount of tweaking of word and character spacing for both paragraphs will fix this, it can't be solved without using split notes.
To use the full range of word and character spacing set minimum to 0 and maximum to 250. Then you can set desired to whatever you want. I don't recommend this but you can do it.

Hi Amy, nothing has changed with word spacing. But you can't enter any value you want - desired (middle) must be <= maximum (right), so if maximum is 100 as shown in your screenshot you cannot increase desired.
The default values for word spacing are 80, 100, and 133. You can enter values from 0 to 250 but minimum must be <= desired and desired must be <= maximum. If you click the arrow to the right of each text field a slider will appear to change the number.

How about another Recolour / HSL adjustment for the background pixel layer only, … as you used already for the entire layer stack? If you nest the adjustment layers accordingly they don't disturb each other.

There are many ways.
Convert pixel layer to image layer. Then you can use the color panel directly to the image layer.

You’re welcome.
In your latest image it seems a bit of a shame that the horse’s head is obscured by the text but if that’s what you want then that’s fine.
I’m also wondering if adding a ‘dual-colour/tint’ effect could add to the ‘drama’ of the scene somehow – see attached image for a bad example – but that’s entirely up to you of course. (Or maybe it would look worse, I don’t know.)

I think that means you are using the Windows version, as it is found under a different menu in the Mac version.
So to avoid confusion, it is a good idea to let us know which version you are using, either in a 'sig' (signature) at the bottom of your posts or within the body of your initial post for each topic you start.

The app preferences has a control for the placement of new Adjustments. You probably want it set as shown below:

"Shift+=" will select the next blend mode for the brush, when you have the Brush Tool selected
You probably did this accidentally

In the context toolbar try changing the Blend Mode from Darken to Normal

From the look of your screenshot, it looks like you have a pixel layer selected. You need to have the mask layer selected if you want to paint black or white on it
 

Wacom is a manufacturer that makes digital input devices such as tablets, pens, etc. iPads can be used as such but that's only a fraction of their design purpose. I'm not an Apple guy so I don't use iPads / iPhones / Macs, etc. but I don't think I'd like using a smart tablet as an input device. Something like a Cintiq 22 (where I could look directly where I'm working, instead of at a monitor) might be great but I'm not ready to drop that kind of cash.
As far as conventional tablets are concerned, I have an inexpensive Wacom Intuos S tablet / pen. I use it for some tasks, but for most it's the mouse. However, when I do use it, it's good enough that I'm happy with keeping and using both devices. Maybe if I locked away my mouse for a year I'd get more proficient with the pen, but photo editing is far from the only thing I do on a computer and a mouse excels elsewhere.
That said, IME how well you have your tablet set up (button assignments, sensitivity, response, etc.) and even more importantly, how much you practice and become fluent with it, will make a huge difference. I'm not phenomenally fluent, but I can get around ...OK-ish. Still, it's worthwhile for me even at that level.

Maybe I've been lucky but I've been using a mouse since the very early '90s and have made a point of having a mouse-level surface on which to rest my mouse arm -- From elbow to wrist. 30+ years so far and no RSI yet. I worked in IT for 24 years and saw soooo many people using those horrible under-desk pull-out keyboard platforms with the mouse extension that pulled out from one side. When I worked on their computers, after just a few minutes of my arm hanging in midair, it would start hurting. Keeping it supported in the neutral position (on an L-shaped desk 'wing' to my right) has worked for me. But everyone is different.

I used to illustrate the old-fashioned way using Rapidograph pens, hand stippling for hours on end. That and 20 years of milking goats and building things using an impact driver have ruined my right hand resulting in bad thumb arthritis and knobby knuckles. I'm very good at using a mouse for very detailed work. I thought of getting a tablet but I can't even hold a pen to write let alone holding a stylus for hours on end. My mouse is a very simple Amazon Basics one that fits my hand well. It feels like an extension of my hand. I don't think about it as being any kind of hindrance. 

I can reinforce @thomaso's problem with tendonitis! I had my first "microcomputer" in the 1970's and didn't switch to a tablet when they became available. I am now suffering.
Irrespective of the technical arguments, I would encourage using a mouse as little as possible for fine work. Having said that, I still use a mouse most of the time - because the damage done to my nerve-endings over the years has resulted in a tremble which is more difficult to compensate for with a tablet than with a mouse.

You’re welcome.
I suspect that the Gradient Map may need to use more than two colours to get it closer to the original but I can’t be sure.
And an Add Noise Live Filter applied to the image might help a bit with the ‘graininess’, maybe.
And maybe a ‘light touch’ Gaussian Blur Live Filter too, perhaps.
Basically, just keep experimenting and see what you get.

You can probably replicate the green/yellow example, up to a certain point, by adding a Black & White Adjustment and a Gradient Map Adjustment – see attached image.
You will need to experiment with the settings of each adjustment to get different results as necessary.
If you want something more specific then you will need to be more specific about your requirements.

You will find a variety of opinions so you'll have to decide for yourself as your experience grows.
After 20 years as an amateur editing photos with a mouse, I read a few years ago that a tablet could replace a mouse completely. Since I sometimes experienced hand stiffness and fatigue with a mouse, I decided to buy a Wacom Intuos tablet as a Christmas present to myself. I put my mouse away in a drawer to force myself to use the tablet for everything. After a week of frustration, I gave up and returned to the mouse, which I can use with either my left or right hand so I can switch hands if I get tired. 
I do use the Wacom for some selection tasks. Right now I am extracting a half dozen people from a busy, complex background of shrubbery, lawn, house, and sky. This requires a lot of manual editing when the selection tools have difficulty discerning edges when contrast is low. It becomes necessary to create a mask and to manually paint on that mask to get precise edges and to eliminate the usual spillover in both directions across the edges. This involves a lot of click-drag maneuvers that can be hard on the finger holding down the mouse button.
I do not like the Wacom stylus. It is far too thin and the small buttons are hard to use. But it is often more relaxing than exerting constant tension on a mouse button.
I find a mouse far more stable to use than a stylus on a tablet. This may in part be due to my aging hands and my deteriorating handwriting skills. 
I think the choice between mouse and tablet will depend on many variables. The issue can be resolved for each person only through trial and error.
Thus, I think it is best not to anticipate every possibility for future needs. Solutions will become apparent as you progress.
For one example of painting on the mask when making difficult selections, see the latest tutorial from InAffinity at
https://www.youtube.com/watch?v=saCIvqBwNMo