Steps to reproduce:
Create a new bookmark with a name containing newline(s). My bookmark example has three lines in total, which happened due to copy and paste. When opening the Edit Bookmarks menu, the view is messed up (see screenshot).
Possibility 1: Do not allow multi-line bookmark names.
Possibility 2: Revise the bookmark menu to display the bookmarks correctly.
Version 0.99.110-beta (WebKit 613.1.12), macOS 12.1; Intel: