For multitracking I imagine Audacity will have pretty minimal functions, like basic merging of separate .wav files into one and the like. There may be more options but I'd definitely go for a dedicated studio application for that. I'd use Audacity mainly for finalising tracks, normalising, EQ, things like that. I have, when I was teaching myself direct wave manipulation, made entire patterns and tracks from existing waves to be used elsewhere but just as an excercise really, the task I set myself was to do a remix edit of a friend's material with no effects or studio programs, using only his wave files, chopping and pasting etc. as one track.
I'm reading mixed reviews about this Darkwave, some say it's great, others not so, never tried it myself so I really couldn't say. Also looked for plugins to allow importing .Flp files that I use but I can't find any.
Tonight I'll uninstall my FLS and put it back in without my license, the packages are all the same for all editions so I'll check out what I can do in default demo mode and see if it would be any good, it says fully functional so, even if actual .flp files can't be shared, exported .wav and .mp3 files could be. That's all we really need, those can easily be imported via audio clip layers, you'd just need to agree on a certain bpm to work on and things could easily be done with whatever patterns and track sequences we shared. I'll go and revert to demo mode and check it out now...