This question is a natural one to ask. I asked it myself several years ago before I understood how MC is intended to be used.
The Media Subtypes are not the intended mechanism for user classification of media. Instead, you can use other fields like Keywords. Keywords can take any value and it is a multi-value field.
So you could assign "educational" and "guitar" to these videos (as an example). You can build a view based on keywords for all of your educational videos. The view can have selections for the types of educational materials you have and let you click on each one to select what you want to see. I've done this with most of my educational stuff and it's pretty nice. I like PANES views for this, but a categories view would work too.
If keywords does not work for your specific case, you can make a new field of your own. Keywords is pretty good for this; I'm just letting you know that you can create your own fields if you want to go that far.
Best of luck,
Brian.
