How to get rid of orphaned tracks&clips in TimelineAsset?

I had to delete a custom track type implementation (due to deprecation), but some existing timelines used those. Now I've got missing tracks on those timelines, which I can delete, but it'll orphan the clips that have been created on those tracks.
Now, on every build, I get warnings that a script is missing for child assets on these TimelineAssets (those clips that haven't been cleaned up properly).

Has anyone got an idea how I can get rid of those orphaned clips? I already tried to get hold of them through the AssetDatabase but it's just returning null references for those clip assets and thus, I can't "destroy" them or delete them. Manually editing the timeline asset file didn't work either, as the clips seem to be restored as soon as I switch back to unity.

 

Did you find a solution?

 

No, I manually cleaned those timeline assets in the end. There may be newer APIs available now though that would allow access to the underlying data