Use the Windows context menu to open Mp3tag by right clicking on a file or folder.
Observe: The Tag Panel directory field is blank. Also, the directory is not added to the drop-down list.
I'm not sure when this behaviour started, but as late as ver 2.85 the directory field was always populated when Mp3tag was opened using the context menu.
I can confirm that behaviour.
The directory field does not even get filled if you select the track.
If you, on the other hand, d&d the same file into Mp3tag, the directory field is filled.