Mr. Mendelli

There currently is no way to do this but several people have requested that it be added, so it might be added to some future version.

On Windows, Designer's dropdown for the tools icon only has 18 of the 21 tools available (excluding the cat tool)
The dropdown does not include "Rectangle, Rounded Rectangle & Ellipse tools, which all have to be added as separate tools
In APhoto all 21 tools are available in the dropdown
@R C-R Is this different on a Mac?

As kind of a lame workaround, what about assigning/using one or more keyboard shortcuts for the ellipse, rectangle, & rounded rectangle tools, & then removing them from the Tools panel? I think the default is "U" for all of them, which cycles through them, but maybe other shortcuts would do. What I have done experimentally in AD is to assign "E" to the Ellipse Tool & "R" to the Rectangle Tool & Rounded Rectangle Tools because it is easy to remember, & tapping "R" cycles between the 2 similar tools.
EDIT: I just noticed that if I tap "E" repeatedly, it cycles between the Ellipse & Rounded Rectangle Tools, even though the Rounded Rectangle Tool shortcut is set to "R."
Anybody else seeing the same thing?
EDIT 2: Quitting & relaunching AD stopped the "E" cycling between the two tools, so now "E" cycles between the Ellipse Tool & no tool selected, & the "R" key cycles beween the 2 rectangle tools.

Welcome to the Affinity forums 
Something that works currently (AP 1.9.3), is to ensure an object that represents alpha is at the top of the stack when you export to an image file.
That object can be a Pixel Mask or it can be anything with its intensity inversely mapped to opacity (black through white mapped to opaque through transparent) and blend mode set to Erase. The mapping can be done with a downward ramp in the left-hand graph of the object's Blend Options.
Below are 3 documents which all export to PNG without RGB being destroyed where alpha is zero.
1.  alpha by erasing.afphoto

 
2. alpha by erasing (simplified).afphoto

 
3. alpha by masking.afphoto

 
Screenshot of a PNG that was exported from from "alpha by erasing.afphoto": 

 
Screenshot of that PNG after filling alpha to prove the RGB was not destroyed:

 
 
 

I will look this over @Lisbon, thank you for the assistance.

Document > Clip Canvas
Respects transparent pixels.

I've been using Affinity Photo more lately and there are a few things I'm still trying to figure out. One thing I use often in Photoshop is the crop to pixels feature, you just make a selection and click the crop tool, the crop tool then automatically snaps to the outer most pixels around the selection then you just apply the crop for a pixel-perfect alignment. I have tried this in Affinity Photo as well as manually cropping and it doesn't seem to be able to do this. In some cases it's easy enough to manually crop, but this is not ideal for anything with semi-opaque pixels or glowing effects where clipping may occur if it is not cropped accurately. Is there a way to do this in Affinity Photo?

I find your statement more than a little over-kind.

You have to authorize with that equally named button first otherwise you can't perform the actions. Further the selected files will be overwritten. - Even if you choose and use the "Save in" option and name the same directory here (in/out dirs are equal) the files will be overwritten. So during my tryouts there was no difference in behaviour here.
There is no interaction performed for those macros, instead their default option values (those during recording dialed in values) are used and performed. So no interaction takes here place at all.
All good points, we don't know until we encounter these in some worst case scenarios!

The built in help file documentation & the two videos @v_kyr mentioned still leave a lot unanswered regarding applying macros in batch jobs. For example:
 
• Assuming one can select files from several different folders for one job & "Save into original location" is ticked, is each file really saved into its individual original folder & what happens if there is a name/filetype conflict with the original?
 
• What happens with macros that offer user interaction, either with a,b, and/or c value sliders or with macro steps that expose one of the available Settings options available from the cog icon during recording?
 
• What can we expect in terms of memory efficiency & CPU use, particularly when Parallel processing is enabled?
 
• What happens if a file can't be processed to completion & saved, for example because the save location runs out of available space or some other process interferes with access to it?
 
Overall, the built in help for both macros & batch jobs is minimal at best & at times a bit misleading, like when the Macros topic says, "Through the Macro panel, you can record any operation in Photo," which of course we know is more than a little over-optimistic.

I have not tried this, or for that matter done anything involving batch jobs, but might it be possible to process one or more image files as a batch job & apply the cropping macro that way?

See also:
AP - Batch Processing (& apply macros) Batch Processing with Macros

Hi Mr.Menelli,
Welcome to the forums.
At the moment the Save option isn't available when recording a macro, it may become available in the future.