Easy fix
1* Crate rolling cache in game, size will be the size you want your manual cache to be
2* exit game and find ROLLINGCACHE.CCC File located (C:)>Users>AppData>Local>Packages>Microsoft.FlightSimulator_8wekyb3d8bbwe>LocalCache and rename it to MANUALCACHE.CCC
3* Start MSFS and enjoy. (A new ROLLINGCACHE.CCC file will be created standard 8g size, also your new manual cache is ready to Rock’n’Roll