SUMMARY If you enable the filter for unused clips in the project bin and you add a clip to the timeline, the audio of that clip disappears in the timeline. If you try to add only the audio to the timeline, you get a error message saying "No available track for insert operation". STEPS TO REPRODUCE 1. Add some clips to the project bin 2. Add some of those clips to the timeline 3. Filter the project bin to show only unused clips 4. Add a clip to the timeline OBSERVED RESULT The audio of the clip disappears from the timeline EXPECTED RESULT The clip is added to the timeline including the audio SOFTWARE/OS VERSIONS Pop!_OS 21.04 Gnome 3.38.5 X11
Thanks for your report! I can confirm this behavior.