I researched to find out if this is a feature already so sorry if I missed the answer somewhere. I'm a long time Photoshop user and this one feature is all I need to make the complete switch away from Adobe. Perspective scaling.
I make videos and overlay perspective text png images to make it look like there is text on the subject in the video rather than on top of the video playback. I export a screenshot, open it in Photoshop, make the text, increase the size, convert to smart object, distort the corners to give it the correct perspective for being on a desired plane, then finally scale the text while staying constrained to the desired plane, then hide the screenshot layer and export as a png. I've been doing this for years and the process is very fast and easy in Photoshop. This allows me to position any bit of descriptive or instructional text in the video like it was always there in real life.
In Affinity photo I use Filter > Distort > Perspective to establish the text on the appropriate plane but after that I have no way of scaling while being constrained to that plane. If there was a way to scale while the perspective filter is active it would be perfect.
Does this feature exist? If not I'd like to request it to be added. I recorded a video to show exactly what I'm talking about:
https://www.youtube.com/watch?v=NeUOXgjGX3g
