Config history needs prompting
The + and X on diag_confbak.php don't explain what they're going to do, and more importantly don't confirm when you revert to an older configuration.
Buttons should be changed to show a hovering description - restore/delete
Both restore and delete buttons need a pop up confirmation box.
A "download config" button next to each revision is probably trivially easy to add while doing this, and would be good to have.