There are a lot of ways to do what you want. This is the way I deal with Music Videos and 3D movies,
First step. In Standard View Video>Files view, add the "fields/tags" you need to work with to the view by right clicking on the column header. Then a popup window comes up and you then add columns for "media sub type" and media type" (and whatever else you want to see) from the list.
For Music Video - this is how I set up my views for Theater View:
To add the "Music Video" item to Theater View:
In Standard View, the screen shot below (Video>Files view), notice that I have added the column "Media Sub Type". The columns in this view show the fields/tags assigned to your media. It's the same data you would see if you clicked on a file and opened the Tag Action Window.
1) Find your music video file, then click on it to select it. In the column "Media sub type" for your file you want to have the value "Music Video". The "Media Type" field should be "Video" To edit this data, click on the file to select it (this highlights the row). You then use the "F2" key to enter edit mode. You can move right and left in the row you selected using the Tab key and Shift+Tab key. When you are in the field "media sub type" for the file you selected, you use the drop down list to select "Music Video".
To add Music Video to Theater View menu:
In my example I have the Music video menu item on the Top Roller (top line) of the Theater View menu. You could also nest Music Video within the Movies menu or Audio menu. It just depends on where (what layer) you add the new Music Video item in the menu.
2) Go to Tools>Options>Theater View. In the section called "Items to show" click on "Add" then on "Library Item".
3) In the section called "Details", rename the "New Library Item" to "Music Video".
4) Then click on "Set Rules for file Display".
5) In the "Rules" box, click the "Add" button to add two rules: a) "Media type" is "Video". and "Media Sub Type" is "Music Video".
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For 3D movies: I sort my 3D movies from the 2D movies by adding "3D" to the "Series" field (the Series filed is not normally used for Movies so it works well here).
In Standard View Video>Files, add the column "Series" if it is not already there. Then find the 3D files/movies and click on one to select it. Use the F2 key to enter edit mode (as described above) and enter "3D" in the "Series" field.
1) Create a new "Library Item" in the "Movies" group (click on "Movies" to select that group, then click "Add" and "Library item".
2) In the section called "Details", rename the "New Library Item" to "3D Movie".
4) Then click on "Set Rules for file Display".
5) In the "Rules" box, click the "Add" button to add two rules: a) "
Media type" is "Video" (actually this is not needed since this view inherits the media type from parent "Video") and "Series" is "3D".