Switching to the first tab in Mail using Applescript or Shell

I am looking for a way to switch to the first tab in a Mail window. It seems like there is no universal way to address tabs in macOS programmatically. I have tried Apple scripting with and without using "System Events", but with no luck. And most scripts on the net are regarding Safari. These do not work:

tell application "System Events" to tell process "Mail" to tell window 1 to tell radio button 1 to click

tell window 1 of application "Mail" to set current tab to tab 1

It seems like Mail handles the tabs as if they were windows. But this does not help since the indexes of the windows/tabs shuffle around depending on how they are set up, whichever tab was selected last etc., and I always want to address tab #1 independent of the window index number and name/contents. I have traversed the Applescript Dictionary but cannot find anything suitable. Any hints would be appreciated. It would also be nice to know if it can be solved using Shell since I am going to use it for a Keyboard Maestro action.