I mentioned this a while ago in another topic, but I think this should really be addressed.
At the VST instrument level, some instruments need to have a note off before the next note on in order to trigger notes correctly in monophonic mode (Tassman, Moog Modular V, Arturia Arp2600 being great examples since so many people have them). While there is an effect command to shorten the note duration (I forget which one), it doesn’t always work (you can’t combine it with Ex, for example), and it makes using these plug-ins more work than they need to be.
It would actually be great to be able to just have a slider in the instrument settings that will allow you to add or subtract a certain amount to the length of notes (probably +/- ticks). This would be great for dealing with monophonic synths that don’t behave, but it’d also be a useful creative tool for creating more staccato and legato phrases without resorting to (respectively) note off commands or multiple note columns when one will do.