If a menu has an entry that is a submenu, and that submenu has entries in it that are also submenus, then the entire menu will close when left clicking the submenu button instead of hovering it.
Some other examples from users:
1. "Add/Import Content" when right clicking a folder in the Content Browser.
2. "Manage Collections" when right clicking an asset (a Material or Blueprint, for example) in the Content Browser.
Menu remains open and users are able to access submenus
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-147209 in the post.