Need to update a skeleton

I added a couple of bones to my character’s skeletal mesh. The new bones have no effect on the existing bones or their hierarchical relationship. The question now is how do I update the existing skeleton and its animations without having to redo everything? (4.19)

Reimport skeletal mesh. It should update skeleton automatically.

Re-importing didn’t work the first try, but for whatever reason it worked when I tried it again. Go figure.

since 5.1 this does not happen anymore.
and the skeleton has no options, such as reimport or re-something-something.

what is suggested procedure now?