Hat Yes, most apps add some saving files.
I don't know the answer to this one. Shouldn't be too hard to check, though.
Hat It work, I can save the picture but I get "An unexpected error occurred after editing" when I press the save button.
yes, that's a known issue. The GrapheneOS camera app shares the file with the markup app, but apparently it only gives access to read the file, not to modify it.