Use direct access [Alt]+ instead of the mouse and the submenus.
Today there is no chance to have Mp3tag embedded in an unattended production batch process ...
... unless you are a master of automated sending of keystrokes.
Someone may willing to go this way to control Mp3tag in such a process ...
... but there is a caveat: the Mp3tag start up time.
The delay time for collecting the system ressources to build up the GUI and such internal processes will be summed up in a batch process, for each start of Mp3tag, and it will consume time.
Another way would be ... start Mp3tag only once and keep it open during the batch process and control it by automated sending the necessary keyboard commands for loading the current file and performing the prepared action.
Note that Mp3tag can be started with commandline parameter ... Mp3tag.exe /fn:"".
Once Mp3tag has been started, at any time a file can be loaded into Mp3tag by this way.
Mp3tag will still behave as a single instance application.
This would reduce the start up time to the minimum.
Somehow, at the right moment, someone has to press the necessary keyboard keys ... [Ctrl]+[A] and [Alt]+ and [Enter].
The batch process must be flagged to wait until Mp3tag has done the action job.
It would be rather nice and productive, if Mp3tag could provide a commandline parameter for invoking a predefined action by its name (mta or mtg file), for example like this ...
Mp3tag.exe /fn:"" /action:""