If you delete a bookmark/folder in #Firefox, you can Undo from the Bookmark Manager if you haven't closed Firefox yet! Whew. They changed where Delete and Add are in the context menus a while ago and I haven't gotten used to either place yet.
They used to run studies that determined the most valuable/used selections and put them first. Maybe they still do and FF demographics changed? It throws me off every time I want to use one.