Hitting the F4 key, will repeat your last edit whatever it may be. This is especially useful for edits that take a number of shortcut keys. Say for instance you are inserting a certain symbol repeatedly; instead of ALT I + S + INSERT and or cutting or pasting you can just put your cursor where you want and keep hitting the F4 key. You only have to do the first edit manually, and from there you can just use the F4 key to "do it again". This is helpful in a lot of different ways (experiment!) and will help reduce your carpel tunnel syndrome.