As far as I'm aware, MC21's built in views under video don't show Media Sub Type. Under Video > Files , I have Media Sub Type as one of my Panes, but I think I added it. ...and that's really the point of my post actually: You can add Media Sub Type to any view pretty easily. If it's a Panes View, you can just right click on a Pane and select "Add Category To Left" (or Right). Add Media Sub Type. Then you can choose by Media Sub Type as part of your Panes filtering.
Or if you want a View that *just* shows Music Videos, you can make that a "rule" for a specific View. As an example, go to Video > Movies. Now right click on that and choose Customize View. Now, Settings > Included Files > Set rules for file display. See how the first rule there says "Media Sub Type is Movie" ? That's what controls what the Movies view shows you!
So you can easily make one just like that for Music Videos. Or for other Media Sub Types. Or several Media Sub Types in one view. Or a Panes View if you like that better. There are just a ton of possibilities in MC's View system. Just add a new View by right clicking on Video and get started.
Play around with it and see what you can get done. If you need some help getting started, tell us what you are trying to see, how you want it presented, that kind of thing, and we'll try to help you out.
Good luck.
Brian.