Regression: Selection in Menu Editor is broken

Working on documentation on onehippo.org (13.0.0 snapshot), I am no longer able to select a menu item below which I'd like to add a new one. Instead, new items always get added at the end of the menu, and then, you have to drag them to the desired location. Trying to select a menu item, the UI behaves as if I want to start dragging immediately. I'm using Chrome v70.

This used to work before the upgrade to version 13, so I assume this is a regression.

It would be nice it there was a regression test added for this use case.