Thank you, @sterndata and @rynonet. I’m the worst sort of wordpress dabbler who knows only enough to break things. ??
But I found the fix (again)! Can I leave this post so if anybody else has this problem, maybe they’ll find this?
Here is a post about how to add link buttons. https://gist.github.com/carrieloves/4b93e84bfda32e1a8811
Turns out, even though the update hid the buttons, the data is still there. So once I put these bits of code back, all the links came back and everything is fine. Yay! Don’t have to redo that part!