I want to specifically, tag certain tabs such that while closing the tab I get a warning.
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Do you mean selecting pinned tabs, also?
Yes. Pinned tabs is doing this job but pinned tabs is doing some part of this but not the whole part it.Lets say, I have a video playing in a mini window and also bunch other tabs open. I have closed the tab that powers the video playing window soo many time while closing rest of the tabs. But not just that, lets say I have an important tab open, when I am quitting (macos command + q) firefox, I want to see a warning.