When using the "Close"/"Close All" options when a report has unsaved modifcations, a warning is shown, but you are forced to save the report or close the window/tab to leave definition file unmodified.

A "close and discard changes" option is helpful and convenient - one can cancel some edits without hoping that a bunch of "Ctrl - Z" presses will clear everything, refer to one report without concern about accidental modifcations (can be editing others), etc.