One way it might work, would be to use the LAN file server feature from the Andoird app (from the launcher go to Options... -> LAN tab). Set the server "/root/" path to be the ScummVM internal folder, which is the "ScummVM data (int)/" shortcut option if you go all the way up the directories with the ScummVM File Manager.
For the new Android port, scummvm.ini resides directly in there --and not under a .config subfoler path.
The LAN server functionality will allow you to retrieve it using a web browser (which should work better if done from another device in the same LAN), back it up and change it -- and then copy it back. At least in theory that *might* work -- I haven't tried to do massive changes to it in that way and re-upload it, and the LAN server feature was not really meant to support updating the configuration file.
Anyway, you should restart scummvm after changing the ini file in that manner.
More info on the LAN feature here:
https://docs.scummvm.org/en/latest/use_scummvm/LAN.html
Changing the ini path to a custom is probably not happening, not by me anyway. I personally spent way too much time last year trying to sort the mess from allowing too much freedom in that regard, which bit us in the butt when Google changed their security policies regarding where apps can and cannot store and related stuff.
It's too much hassle to keep up with all the options and what older Android versions allowed, and I wouldn't want to create the same nightmare for the future developer who'll maintain the mod.
Honestly the fix-up code just to support upgrading from the old Android versions was a nightmare to produce and test, and the end result is far from a beauty too (and has a heavy impact on startup performance).
Sorry for the rant above. Just felt that I should explain where I'm coming from on this issue.