When you click on this button, you get a large window that opens, and of course shows what styles you have available. The window itself has a "blank" area in the bottom right-hand corner. I wish that area contained a brief "index" of what the style "prefixes" mean. (Just a brief reminder)

That is, something like this:

* indicates ???
^ indicates ???
= indicates ???
_ indicates ???
M_ indicates ???

etc.