Despite the advice on this question on the forum, the sidebar appears whenever I open Firefox, regardless of whether it's set to display bookmarks, history, or synced tab…
Despite the advice on this question on the forum, the sidebar appears whenever I open Firefox, regardless of whether it's set to display bookmarks, history, or synced tabs. And the "Show Sidebars" icon is glued to my toolbar (the one with the URL & search fields). Whenever I go to Customize and drag it out of there to the Customize box, where the unused icons live, it reappears every time I close and reopen Firefox. BUG.
One piece of advice on the Forum from 8/8/18 says to "Right-click a bookmark and choose Properties, then check in the lower left corner for a checkbox to "Load this bookmark in the sidebar" and uncheck that box." I have no such checkbox on the bookmarks I've right-clicked, so I obviously can't uncheck it. Besides, this would require looking at every bookmark - grossly impractical.
The other advice on 8/8/18 also doesn't work. It says to rename or remove xulstore.json in the Firefox profile folder. Doing this makes Firefox open without remembering much of anything. This is going after a fly with a sledgehammer.
This should clearly be in Options. It is a constant annoyance to have to click the X on the sidebar every time I open Firefox.