michaelalala - if you do this, any event property that is the SAME for all selected noted will be displayed in the Event Viewer.
If any of the events have more than one value you'll see a little + sign in the relevant box
But yes, you can change them all there as well.
One caveat - if you select a bunch of notes with varying velocities and you want to make them all 100, if the FIRST note in your selection is already 100, it won't work.