I can confirm that it MSFS 2020 (Windows Store version) works with Sim Commander. I had to do four things.

1. Take ownership of the WindowsApps folder. That’s what Mr Villers suggests above. If you need additional guidance, Google ”WindowsApps access” or similar. As Mr Villers suggests - use caution and make sure you know what you are doing before doing it.

2. For some reason SC4 did not autodetect the game. Add the game manually in SC4. Don’t choose the MS Flightsimulator executable. Select the gamelauncherhelper inside the MS FlightSimulator X folder in WindowsApps.

3. After adding the game manually, SC4 did sutodetect the game. I kept the autodetected profile and deleted the other because the autodetected profile contains the game default effects. Otherwise they have to be added manually.

4. After launching the game, SC4 didn’t detect that it had started. In order to solve that I had to add the flightsim executable in the ’Wait On’ section of the advanced game settings. The name (no path needed) of the game executable this time, not the launcher. Again in the MS FlightSimulator X folder in WindowsApps.

After those measures, the game works fine for both my GS-5 and my G-Belt. Tuning is of course needed as we all have our own preferences. 

Hope this helps someone.

Sim Commander should detect it if installed in the default location and if you are an administrator on your PC.

Some time ago, Microsoft started preventing consumers from accessing the folders of apps installed by Microsoft Store. There is some way to regain access to the actual files and folders by taking ownership of the folder, but it's an expert level task and can wreak havoc on your system if you get it wrong, so it is not advised. 

If Sim Commander isn't detecting the Microsoft Store version for you and you are an admin, your best bet will be to get the Steam version unfortunately.