"Subscribed Forums" -- that choice would lead to a page which
listed only the forums that I have subscribed.  

That's what the "my forums" link does!
I have only subscribed to the one's I'm interested in and those are all that show under that tab so if I'm understanding what you want right, it's already there!
You need to set up your forum options and then they appear in that tab!

Injustice will be avenged.
Cofiwch Dryweryn.