Hello,
I first had the same problems with not getting access to the windowapp folder and could not use the dlss swapper with my Msfs store version.
Then I learned the solution in a video:
Move your msfs store version with the Xbox App on your computer(manage files option) to the xbox game folder. Then you can use the dlss swapper and easily update your dlss file.
It worked very well for me.
Best regards,
Tris