(Audacity 2.0.3 or alpha-5-June, Windows 7, any machine)
Editing a long single stereo track with one label track, I demarcate a song by ear (using [ and ]), hit CTL-B, type a label number and press ENTER. Then I press SHIFT-UP to focus on the music track.
Now I apply some Effect, say Equalization. I listen to the result, dislike it, and hit CTL-Z (or Edit > Undo Equalization). But Audacity doesn't simply undo the Equalization!
It returns to a curious state ready for me to type into the last label, which is white. So I must focus on the label track, hit ENTER or ESC, then focus back on the stereo track, each time.
Illogical? One would expect simply to undo the last Effect?
(Audacity is so good that now I'm expecting perfection.) Tony