android 10 – How to select photos for opening from inside an app with a certain tool?

I am converting hundreds of A4 pages of handwritten text into computer text with the amazing Pen to Script app on my Android 10 phone. I got many more to process and I go crazy on one detail:

Here is my problem: Every time I start a new page, I have to select its photo from a very full folder. But every time I get offered some useless (for this purpose) “app switcher” (I am not sure that is its correct name) where I see recent photos and a choice of several apps to select photos.

Problem is also that at thumbnail-size on a phone, all pages of handwritten text look the same. So I need my trusted Total Commander app, which is showing me file names, rather than previews.

Now I am asking on how to tell Android 10 (or the Pen to Script App) to forget the app switcher and let me use Total Commander whenever I need to select a photo.