thanks Ashley and Tokinsom, these solutions will be a great improvement for working on large projects!
if layer "parent" as sub-layers "foo" and "bar", and you rename "bar" to "baz", there doesn't seem to be any way to tell this apart from deleting "bar" and adding a new layer named "baz".
That's interesting that it's tricky for renames to apply across multiple layouts.
What if there was a hidden internal unique ID for layers? So it doesn't have to assume that a rename was a layer deletion, because it can see it still has the same ID.