You can open the bookmark sidebar with the keyboard shortcut Ctrl + B. More information about the Firefox sidebar can be found in the Use the Firefox sidebar to access bookmarks, history and social features support documentation.

When I open the bookmarks icon it shows the ability to hide or show the sidebar. Clicking on that does nothing.

HI, please go into CCleaner and adjust the preferences to ignore Firefox System files and Folders.

• https://support.mozilla.org/en-US/kb/firefox-sidebar-access-bookmarks-history-social

Please see the answer given below :

• https://support.mozilla.org/en-US/questions/1214647

Please let us know if this solved your issue or if need further assistance.

Try to rename/remove xulstore.json and if present delete localstore.rdf in the Firefox profile folder with Firefox closed.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox