When you combine instruments to a kit that have initially been split among multiple players, the mixer drops the lanes for the single instruments and no new lane for the new kit is being created.
Steps to reproduce:
- Start with empty document
- Add new player (snare drum)
- Add new player (bass drum)
=> Result: Mixer has separate lanes for snare drum and bass drum.
- Move bass drum instrument to snare drum player (drag & drop)
- Select “Make into kit” (“Instrumente zu Kit kombinieren” in German)
=> The lanes for snare drum and bass drum disappear from the mixer, but no new lane for the kit is being created.
I hope this helps,