Hello,
I imported a midi file, and have it playing with Dimension, but I can't move any notes in the piano roll or any other view. No tool will work. I cannot select either. Is there some sort of lock on the file?
 
I loaded a different file and this one's notes will edit but only some of the notes play, and which ones do will change. All velocities are within decent volume range to be heard. The notes will sound when the smart tool is clicked on them, but then some will not sound when playing . Whew, I want to like this program ...
 
Thanks in advance!

Check the range of the notes. Dimension Pro's patches have "active keys" for each. I am suspecting that your MIDI files are falling outside of its "active key" range.

Random skipping of MIDI notes is usually due to undersized MIDI buffer in "MIDI buffers, prepare using xx ms buffers". Double the buffer size, and that might fix it.
 
About that file with all notes locked, I don't know. If the clip is not locked, and the correct track is active, then I don't know what it could be. I don't know if it's possible to lock the MIDI-file itself uneditable. Even if the notes are outside the instruments key-range, the notes should still be editable.

Thanks much for your responses! I can only compare various DAWS with the same files--Podium, Reaper, Mu all work outa the box, and tho the notes sometimes were out of the instruments' range, the files were editable.  I'll stick with Reaper for now (whose interface is equally inscrutable to me!), and accept the blame for not getting it. Thanks again.