In v8.8, the tab bar settings were moved to their own page of preferences, no longer in General.
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See the v8.8 release notes or the user manual.
Occasionally, preferences are moved to a different or separate page of the dialog, because new options require more room than exist on the original page – for example, recent additional tab bar settings made it impossible to fit them all with the “general” settings, so they were moved to their own page, so that there’s room for them again.
The User Manual tries to note all of those moves, so if you have a preference that you cannot find, just search for the preference text (like last tab or exit on close), and it will tell you where it moved to, and where it used to be. (After a few years, the “(changed in vX.Y.Z)” is removed, to avoid too much clutter; but we try to make it easy to find.)