I'am aware of this but is this option about which tags musicbee is reading and showing? I think is not because musicbee still prefers to show ID3v1 over ID3v2 if both are existing on a file.
In files that have both ID3v1.1 and 2.3 in my library, MB defaults to showing the 2.3 tag in Edit (which I have selected for write priority in the place phred mentions). The only way to tell within MB if a 1.1 (or an APE) tag also exists in the file is to use Tag Inspector (vs. just Edit), and check the appropriate tag type box, where it will then appear if present.
The external tagger Kid3 will default to showing all existing tags, including their contents, when opening a file. IOW it doesn't have a "read priority" like MB or Mp3tag, it just shows it all. Adding that as an external tool is an easy way to spot multiple tags.