See video below for details. I click on a different object in the explorer to change the focus which causes the bug. If the animation editor window loses focus when no keyframes have been added yet, any body parts that were added will be removed upon refocusing the animation editor window.
Expected behavior
When the window loses focus I expect that all body parts that I added will remain added after refocusing the animation editor window.
Hi there, thanks for your report!
This is actually working as intended. The ACE prunes empty tracks when saving an animation. When you switch to another rig (or you select an instance that is not a rig, and therefore the ACE deactivates, as in your video), your work in progress is saved and then restored when you come back to the first rig. That is why the empty tracks disappear.
If you added keyframes to some of the tracks, then coming back to the rig would correctly restore those tracks.
What you can also do is add all the tracks, right click on the summary track (the track that is shown in a darker grey at the top of the dopesheet) at timestamp 0 and choose “Add Keyframe here”. This will add a keyframe to all tracks, preventing the ACE from removing the tracks you added.
Cheers!