Is it possible to run simcommander 4.5 for the none steam verion of msfs2020. I have tried to point to the game exe file but it says that it cannot be accessed by the system. thanks
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.