How to use Cloud Gaming when the Game is already installed but need to transfer

Hello everyone, I have the Problem that i cannot use the Cloud Version of an Game (in this Case Witcher 3 from Gamepass) when i have the Game already installed but not transfered to the S/X storage in lack of Space its on an external Hard Drive because the time i played it doesent have an S/X Upgrade.

So when the Game hits Gamepass i think "oh cool i can Play this over Cloud now" but it says sorry you have to transfer it to intern storage...

How to solve this Problem without uninstall the whole Game?