To open the Bookmarks Manager, press the Alt or F10 key bring up the tool bar, and select Bookmarks. Hot key is <Control>(Mac:<Command>) <Shift> B.

Use the search bar to find that bookmark and click on it. Its properties will be displayed at the bottom. Turn off the sidebar option.

On Windows, you can right-click the bookmark on the menu to access that Properties dialog. Not sure whether right-click/Ctrl+click works there on Mac or whether you need to use Fred's method.

Note that opening the bookmark in the sidebar is the default for bookmarks that are created via a link or button on a website.

On Mac you may have to check the "Load this bookmark in the sidebar" setting in the Details pane at the bottom right in the Bookmarks Manager (Library). Click the "More" button to reveal this setting.

• Bookmarks > Show All Bookmarks

• https://support.mozilla.org/kb/how-do-i-use-bookmarks

FredMcD said

To open the Bookmarks Manager, press the Alt or F10 key bring up the tool bar, and select Bookmarks. Hot key is <Control>(Mac:<Command>) <Shift> B. Use the search bar to find that bookmark and click on it. Its properties will be displayed at the bottom. Turn off the sidebar option.

Though the Alt (nada) or F10 (volume on/off) didn't help here (OS 10.10.4) , I did find the extension of the properties drop down for each bookmark which in turn revealed (Ta Daa!) the "Load this bookmark in the sidebar" check box. How any of these got checked (only the Mozilla god knows) but thanks for pointing me in the right direction Fred!

Glad to help. Safe surfing.

Note that you can use the SQLite Manager extension and execute this SQLite code to find bookmarks that load in the sidebar: Open the places.sqlite database file.

SELECT b.id AS "Bookmark ID", b.title AS Title, f.url AS Url, p.title AS Folder, ia.content, aa.name AS AnnoAttribute
FROM (moz_bookmarks AS b INNER JOIN moz_bookmarks AS p ON p.id = b.parent), moz_places AS f, moz_items_annos AS ia, moz_anno_attributes AS aa
WHERE (b.fk = f.id) AND (b.id = ia.item_id) AND (ia.anno_attribute_id = aa.id) AND (aa.name LIKE 'bookmarkProperties/loadInSidebar')

• https://addons.mozilla.org/firefox/addon/sqlite-manager/