I would suggest reading the wiki section on multiple artist spitter (it's on the tagging page) and also looking at your example track with the Tag Inspector.
Artist, Guest Artist, Performer, Remixer, and Display Artist are all written to different tag frames (name of the tag in the file). Artist is a standard frame used by almost all music software. Remixer is also a standard frame (ie, defined in ID3v2.x tag standards), but not always supported. Performer, Guest Artist, and Display Artist are non-standard frames that would only be picked up by other software if it is designed to read custom TXXX/ frames (for MP3, at least).
Edit: well, let me correct my first answer to say that you can in fact add any name of tag you want, up to the number of custom tags available in MusicBee. But those won't show up in the multiple artist splitter, they're just shown in the tag editor. And like Guest Artist and Performer, they probably won't be shown in other programs.
You can define the tags in the multiple artist splitter as custom tags, too (i.e., define TXXX/PERFORMER as one of your custom tags), but that causes weird programmatic issues sometimes