I'm iterating on my skeletons a lot and one of my main issues I come across frequently is the spawned Skeleton Utility bone hierarchy not being able to update without completely removing it and spawning a new one. My specific use case is applying about 25 physics scripts on various bones for secondary movement such as hair, ears, and tails. These scripts also handle applying different settings based on the active skin. So when I update something on the Spine side such as adding new bones or renaming existing bones, I have to nuke the work I've already done and start the setup again.
A workaround I was using recently for new bones was to spawn a second Skeleton Utility's bone hierarchy and drag the new bones to the first hierarchy, then remove the second hierarchy. This seemed to work for a while until I updated Unity and Spine Runtimes and the bones I had done this for were completely out of position. Had to redo the prefabs entirely.
So a button that would scan for new bones which currently are not in the hierarchy and then add them would be a godsend. Bonus points for the same button renaming existing bones according to changes in Spine.