Clarification: using keys to set duration etc., does not work if a separate piano roll window is the focus for entry or editing. Step entry can only be done in a piano roll editor within the main tracks window, and the duration selection keys work ONLY if all other numeric key assignments have been deleted (otherwise it keeps switching among screensets). If you focus on the editor window to make a correction, the step entry key shortcuts stop working until you again manually focus on the step entry window. Using the sustain pedal to extend notes works sometimes, sometimes not.
This is a cumbersome mess - is it really supposed to work this way? I hope there's a 10.4.5 coming soon with a bit of sanity.
Also, LPX seems unable to distinguish the numeric keypad from the number keys on the main keyboard. YMMV, since I am using an aftermarket keypad rather than the overpriced Apple model.