Short of doing a refresh I do not know myself how to fix your date sort. Something is a little wrong. History/Bookmarks does not have to be in the Sidebar, it is what you choose or what it decided to default to you for some strange reason. Possible another reason to refresh. If Mouse to top of browser and click an blank space then Right Click and click Menu Bar there seems to be a few more commands as well as Restore Previous Session which is missing from the 3 Bar Menu. I think by the sounds of it you should have a look at this : https://www.howtogeek.com/333805/how-to-change-or-customize-firefoxs-new-tab-page/ and https://www.howtogeek.com/333110/how-to-customize-firefox-quantum-and-remove-the-white-space-around-the-title-bar/ You can drag the Library (and +++ ) out to the bar beside Extensions or where you want from Optimize. If wanting to refresh as sooner than later would be better : Please : https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer and https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles then https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings TEST....... If no issues then Extensions which need to be added back in 1 at a time and tested ..... Or it is your Profile : Make a new one and test ...: https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Note: Any customization will revert back to default, you will also need to reinstall Extensions. Please let us know if this solved your issue or if need further assistance.