I marked a question as "favorite" using the star icon on the left. I now want to go back to it but can't work out how to list my favorite questions. Can't find anything in help either!
If you go to the Activity tab on your profile—
— you will see a favorites link in the list of subtabs about halfway down the page:
(This does seem a little clumsy, and perhaps this is why I have never used the favorite questions feature. Favorite tags, in contrast, are accessible directly from the sidebar.)