I get tons pictures from my students’ works.
So I’d like to open several pictures or documents from Files as pages of one single document.

So far you can select and share them in GoodNotes, but then I’ll just get many single documents with one page each.
So here should be a dialog like „Open as separate documents“ or „Open all in a single document“ or „Add to document“.

You could open a new document in GoodNotes you want to have the pictures in, go to Thumbnail view, go back to Files and share the pictures in GoodNotes (then you’ll be asked if create a new document or add to existing document) - but going around Thumbnail view is a bit of a hassle.
This workflow can be easier.