Uh-oh, Recently Bookmarked is just a reverse-chronological list of your current bookmarks. If you delete from there, you are deleting your bookmarks. To "undo" deletes, you can try the Undo command in the Library window. Either:

• Ctrl+Shift+b
• "Show All Bookmarks"

At the upper left, under the Organize menu, check for Undo.

As far as I know there's no way to remove the Recently Bookmarked section from the "Library" menu. However, there is a different button you can use for bookmarks if you prefer.

(A) Use the Customize panel (Customize Firefox controls, buttons and toolbars) to drag the icon to the desired spot on the toolbar

(B) Use the method from Bookmarks in Firefox - section entitled: How do I add the Bookmarks Menu button to the toolbar?

• Click the "Library" button:
• Click "Bookmarks"
• Click "Bookmarking Tools"
• Click "Add Bookmarks Menu to Toolbar"

In the Library window ("Show All Bookmarks") you can remove the Recently Bookmarked "smart folder" if you don't want to see it. Don't remove its contents. Instead, right-click Recently Bookmarked and choose Delete.

If you already have close and restart Firefox then you can't use Undo in the Bookmarks Manager (Library) and you will have to use restore in the Library to restore a recent JSON backup.

• Bookmarks -> Show All Bookmarks -> Import & Backup -> Restore

The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once. You also see this count in the Restore menu drop-down list.

• bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4.

You can hide this folder with code in userChrome.css.

• [/questions/1220764] How do I remove Recently Bookmarked from Firefox 60.0.1?