fr: add busses from mixer

[autumncheney]

this would make mixing a lot easier. of course there should be an option to automatically make the new busses invisible in the sequencer

[kjetil]

Yes. Implemented now. Going to be available in the next version. For now, newly created buses from the mixer is invisible in the sequencer. I think that's what you normally want.

[autumncheney]

yay!!