In the last months, we changed the saves location to your Document folder (that's why the game asks for the folder permission).
You should have a renpy saves folder in Documents with subfolders under it.
You can copy/paste saves files from between folders as you want.
Achievements are stored in the persistent file, which should be in these folders too
It's not up to date but still has useful information:
https://wiki.andrealphusgames.com/wiki/How_to_find_a_save_file