A recent similar thread (but no solution I can see)
Just today I inserted some 40 labels with [Ins] and auto increment. In older KiCad versions, inserting those labels was as quick as my keyboard repetition rate. In later KiCad versions labels keep getting added for a second or two after I release the [Ins] key. It is a slight annoyance but if I had to do this more often then I’d probably train my muscle memory to release the [Ins] key quite close to the time that results in approximately the right amount of labels. (I find deleting extra labels much quicker then adding one more after a mistake).