So if you play offline, as in not through the Epic Games Launcher, then the save files will either be placed in the common folder or in the folder that was last associated with your last login to the game.

I don't see some of my save files in the game.

So since save files are now associated with your Epic account ID, you will only be able to see save files that are associated with said account.

So if you played on another account on the same computer, you need to either log back into that account or move the save file to the folder corresponding to that Epic account that you want to be on.