Great Add-on!

Suggestion (please): The same behavior modification is needed in another critical location... the Library window (Ctrl-Shift-B). In this window, Firefox now defaults to selecting "Other Bookmarks" in the left pane... and that's a real pain :)

This auto-selecting of the last entry on the list (Other Bookmarks) doesn't seem logical.

Now I have to select a category in the left pane, and then tab or click over to the right pane.

The Library's behavior should be corrected to once again select "All Bookmarks" by default in the left pane, with the focus initially set in the right pane to the top selection (Bookmarks Toolbar).

Tried the support forum, but unfortunately, no replies...
https://support.mozilla.org/en-US/questions/1203150

Figured this was a natural for the Default Bookmark Folder Add-on :)

Fantastic job as it is... saved my sanity!