If dont have a global file, with any saves you download you can still run the game then start a new game, save the game, then exit out of the game, reload it and try save files. By doing this it creates a global file, allowing the game to recognize that there is in fact save files present in the save folder.
Its also important the save files have their proper name. Sometimes users who upload save files attach names to them. IE Frog.rppg, when it should be renamed file5. Or whatever number slot you want to use. Starting a new game and save it, then looking into the save folder will show the name of the save file, RPG uses (depending on the version a dev uses) have different named save files.
Ive used this technique and still do and it has worked, being compressed or not, that doesn't really matter, but sometimes compressed games have flaws/bugs that could cause issues.