I'm wondering about this too. I am likewise, trying to scrape by with 32GB on my iPad Pro and trying to get rid of unused files, but I can't seem to figure out where these Affinity Photo files that show up in the Inbox folder in iTunes, when the iPad is connected to my iMac, reside on the iPad and how I get rid of them.
As you can see, I have already closed and deleted all my files, leaving only the sample, tutorial files that come with the app:
I don't have the huge size problems some are having, the app is taking "only" a GB for itself and there are almost a gig of other documents somewhere:
When I open iTunes, it shows the Inbox folder has about 300MB of files:
Dragging that folder to my desktop shows there are brush files and library files, but also regular PSD files that have long since been deleted, but that still are somehow taking up space on the iPad in this folder:
None of these are shown in the Files as being on my iPad files, I don't even show an Affinity Photo folder there at all:
So, why are these layered files still taking space up in this Inbox folder, and how do I get rid of them, short of deleting the app and reinstalling it and all my purchased brush sets, etc.?