Hi, please reset this to true if is false About:config search for : browser.tabs.warnOnCloseOtherTabs

As for changing keys that is not possible at this time. https://support.mozilla.org/en-US/kb/keyboard-shortcuts-perform-firefox-tasks-quickly

Please let us know if this solved your issue or if need further assistance.

Yeah, that's on True as well.

Note that Ctrl+Shift+T is the keyboard shortcut to reopen a closed tab similar to open a new tab via Ctrl+T.

Firefox might not show a warning when the startup setting is to reopen tabs automatically (Show my windows and tabs from last time). Note that this is still the safest startup setting to prevent losing tabs in case Firefox crashes or otherwise doesn't close properly.

Yup. I'm well aware of that.

I think the problem is that Firefox ignores all the "*warnOn*" tags when it's configured to reopen tabs automatically.

IMO, this is taking control away from the user unnecessarily.

For security reasons, I've configured my firefox to delete all cookies on exit, and i use a master password, so restarting means i have to sign in all over again and this frequently means 2FA - all of which can be a PITA when you keep killing the browser by mistake.