Hi faxeGotBan
I am Dave, I will help you with this.
The WindowsApps folder is the most protected folder on a Windows system, that is done to ensure the pre-installed Windows apps and all apps and games from the Microsoft Store are protected from malware.
Microsoft recommend you do not change permissions on that folder, because many users have corrupted their Windows operating system by doing that, or at the least, all Store apps ang games will stop functioning.
If it is enough to find the location of a game exe file, here is how to find that location
Open Tas manager (Ctrl + Shift +Esc) then select the Processes tab
Right click any column header and turn on the Command Line column
Then open a store game and in the Command Line column you will see the exact path to the game exe, which you may be able to add to the Steam Launcher.