Edit Point Type [U] is only useful after using Select Nearest Edit Point [V] first.
Hit V and the nearest part of the clip to the playhead will turn green. Now pressing U selects between three point types; the end of the previous clip, the beginning of the following clip, or the meeting between the two. The GIF below illustrates pressing U in succession:
click U after V a couple of times in the timeline
To truly get the most benefit out of Edit Point Type, I'd highly recommend getting comfortable with Trim Edit Mode [T] first. Having the knowledge of both shortcuts will allow for less reliance on mousing, which will in turn be much easier on your hands. And hurting your hand from using the computer too much is simply not a cool story to tell.
Hit up the User/Keyboard Mapping in Preferences when you're ready to assign your own keyboard shortcuts.