Mobile versions of Firefox have no fast gesture, command or button to close a tab. The user must first click the Tabs button and drag the tab away
Some websites (for example, real estate classifieds) open a new tab for every item clicked, which makes navigation cumbersome in Firefox for mobile.
One simple idea that would make such navigation easier would be if, when a tab has nowhere to go back (no history), the back button would be replaced by a “close tab” button instead of being greyed out. This would make use of the muscle memory we already have for when we want to go back.
The same logic could be used for the “swipe from left edge” gesture on iOS and the “back” button on android phones.