StyleEdit can be confusing when you first launch it because it opens to a text window with what looks like text that you can edit. The program appears to be dead until you can edit the text. You can edit the text, but you cannot just click on it to select it.
There are three ways you can edit the text:
1) Choose "Text" from the "Edit" menu.
2) Hold down the "Command" key and the "Y" key.
3) Double-click in the text window.
Doing one of these things will bring up a separate text window which you can edit. (The window looks like at text window you might see in a program like Adobe Photoshop.)
The reason two separate windows are necessary to edit text and view text is that the Apple Media Tool does not currently support "rich" styled text. In other words, you can't mix fonts, point sizes, etc. in the same text field. StyleEdit uses a text-entry window like Photoshop to force users to confine themselves to one style at a time. The reason why rich text is not supported that rich text does not work well in a cross-platform environment.
If you want to utilize rich text and do not care about cross-platform issues, then you can modify TEXTHANDLER to use TEStylHandles instead of TEHandles and add some routines to change parts of the text to different styles.