Ctrl_Tab switches tabs but does not switch to new tab's group and highlight the new tab
When previous tab was in another group, that previous group stays open, the previous tab is de-highlighted ... have to hunt through groups for the new active tab's location by manually clicking groups, which adds each active tab in each group clicked to the Ctrl_Tab stack... after 4 you have lost the ability to ctrl_tab to the tab you were trying to locate.
(maybe there is a workaround to increase the initial Ctrl_Tab stack before "show all 386 tabs", (which do NOT show in order visited) - question posted at https://support.mozilla.org/en-US/questions/1219054)
(A "preview" type facility as suggested at #109 might be another workaround)