For all MC users:
ok, I now managed to do it this way:
1) A PowerShell script that starts the MC App with command line parameters:
# Despite the -WindowStyle Hidden parameter, the PowerShell window still pops up briefly.
# Therefore, I am starting this script with a separate vb script.
# For some reason, with the vb script, I can avoid any window to pop other than MC itself, which was not possible with the PS script.
$appPackage = "48089MathiasSvensson.MultiCommander_9d7x1c4ybj2dr!MultiCommander"
$arguments = "-AutoRun=_UDC_runAt_MC_Startup"
Start-Process -FilePath "shell:AppsFolder\$appPackage" -ArgumentList $arguments -WindowStyle Hidden
Hint: I had previously tried to start the MC App with a shortcut using eplorer.exe (something like "explorer.exe shell:AppsFolder\[MC app folder]![AppId] [parameter]") but in this way it would not work to hand over any command line parameters. It would start the app without parameters, but as soon as I added them it would not even start anymore. I tried all kinds of variants with the quotes, but the only solution that I finally found was to use the PS script.
2) A VB script that starts the PS script in order to prevent the PS window from popping up:
' MsgBox "Just for testing: VB script started", 0, "VB script started"
Set objShell = CreateObject("WScript.Shell")
objShell.Run "powershell.exe -NoProfile -ExecutionPolicy Bypass -File ""[name of powershell script].ps1""", 0, False
3) A shortcut to the VB script in order to be able to pin it to the task bar:
Target: C:\Windows\System32\wscript.exe "[path and name of VB script].vbs"
Hint: I found out the hard way, that for some reason it is possible that the task bar does not like shortcuts with defined working directories that deviate from the path in the target definition.
So, the PowerShell does the heavy lifting. If you are ok, without the option to start it from the taskbar and are ok with the PowerShell window to pop up briefly, then you only need the ps1 script.
And regarding the taskbar, unfortunately there is a drawback, that can not be changed AFAIK. Since the shortcuts points to wscript.exe, it will be a separate item on the taskbar and the actual MC item will pop up or exist next to it, ending up in the shortcut item that starts MC and then MC (when its running) on its own with a separate item. Not really pretty, but I found no solution. So far, I personally rather have the starting shortcut in the taskbar, and live with the fact that the running MC item is next to it, than not having the starting shortcut in the taskbar.
regards, m.