How should I go about dealing with threesomes when I'm uploading fic? In the past, repeated attempts have just resulted in me being faced with errors telling me "Pairings is invalid". Usually my stopgap is to just fill all three characters in at the "Characters" field, put, say, "Character A/Character B, Character B/Character C" in the "Pairings" field, and then tag it with "Threesome", but this seems like a somewhat messy solution. Whether I try with "Category: Multi" or "Category: Other" doesn't seem to make a differences (all of the ones I've tried it with have been mixed-gender threesomes, so simply selecting the M/M, F/F, or Het categories doesn't seem appropriate, and attempting to choose "Category: Het", then "Pairings: A/B/C" returns the same error message as before anyway). Is there something very obvious that I'm missing?

(Alternately, is this something to put in the Feedback form at the site, rather than asking about here?)