if you scroll down, indivi said:
"Windows: C:\users\(username)\AppData\Local\UserData\Default\Lust Doll Plus
Mac: \Users\(username)\Library\Application Support\Default\Lust Doll Plus
Linux: \Users\(username)\.config\KADOKAWA\RPGMV\Default\Lust Doll Plus (May need to sudo nautilus if you don't have access to .config)
Android: \data\data\indivi.indivigames.lustdollplus (Requires root access)
If you're on android, don't uninstall before installing the new version. Otherwise, your save file should transfer automatically!"