What's the sense of having to open the XBox App to start MSFS? Is there a way to just add MSFS to the task bar like every other Flight Sim version in the past?
You have already found the way to trigger the sim directly, but I'd like to give a small warning (more like an answer) linked to the very first part of your question.
I'm using the Steam version of MSFS, so technically I don't need to launch the XBox app at all for my MSFS. But I do it anyways.
The reason is simple: launching the XBox app gives me a very quick and easy way to check if my account is correctly logged in to the XBox Live network.
When there's a problem, the XBox app shows it right away with a nice warning banner at the top of the screen.
If the account is not connected/logged in correctly, and I trigger the sim anyways, then it will reach the "checking for updates" loading screen and it will ask me to download 100+ GB of data because it forgot I actually have the sim installed already. And it forgot where. And if I tell him where, then it might lose all of my settings.
Of course, when this happens, I just kill the sim right away, go to the XBox app, see that there is a warning, then I proceed to disconnect and reconnect my account, and relaunch the sim that suddenly got all of its memory back...
Launching the Xbox app before launching the sim saves some stress and time.