You can toggle as hide/show bookmark's titles on bookmark toolbar.
Download addon from below URL.
- Click icon ore press shoutcut key (Cmd+Shift+Y) therefore toggle hide/show titles on bookmar toolbar.
Just to be sure please back up your bookmarks.
Because this addon is editing bookmark information directly.
If the browser crashes while the add-on is manipulating bookmarks, the bookmark information may be wrong.
Please sending an issue or pull-request on this repository.