NotMyFault

reasonable combinations are described here

Use the channels panel, and inspect the „pixel selection“ thumbnail. There you can see what is selected. the marching ants are invisible when everything is selected. another test is to switch mode to subtract, or invert selection. or create a mask, or switch to quick mask mode and choose black or white. all these methods show what is really selected. Marching ants show only crossing of 50% transparency line, often giving false impression.

The shapes should have „no fill“, and the stroke color must be any other than black.

Even simpler: blend mode add will do the trick. To achieve the target colors, use any suitable adjustment, e.g gradient map.

In this specific case, I would use a simpler trick: use 50% grey as color for stroke use blend mode multiply add a curves adjustment which only allows 50% grey to be shown as black, all other colors as white (or chattier background you like)

This sounds a little bit like „xor“ blend mode. I made a tutorial for that:

See

https://affinity.help/designer2/en-US.lproj/pages/Workspace/preferences.html section „user interface“ Decimal Places for Unit Types Controls the number of decimal places allowable for each document measurement unit and degree readouts.

If you want to treat a pixel layer and a nested mask as „one object“, rasterize is an option. The mask will be used as alpha channel, so all selections and move actions will impact both. note this is a destructive operation, please make a backup of your file before trying.

You can configure decimals in settings for all document units seperatly

To be more precise: if rasterize did not solve the issue, we would really really need a sample document to reproduce what is actually going on. Please, we beg you.

It is. Just rasterize one single time again in the current rotation, it will 100% solve the issue - at least the issue that I could read out of your description without having access to a sample document.

Strong ego? you don’t need to share any production file. Just made up something roughly same shape. What looks like a perfect description of facts from your perspective might be not sufficient for readers/readers. A sample document is always great.

You can rasterize multiple times. But try to use fresh (unrotated) copies and don’t repeatedly do a sequence of small rotation and rasterize.