Original Q: Searching within my favorites
@Braim's saying to do the following in the site's search boxes to get what you want. If you tell the search
infavorites:<SE user #> followed by either text or a tag,
[bash], for example you'll get what you want.
See the example below which should help.
Updated Q: Favorites manager for stackexchange favorites?
Unfortunately there doesn't appear to be any method for "managing" favorites. You can bookmark them within your browser and manage them externally from the site. There might be a way to "export" them from the site and "import" them into your browser's bookmark manager as well.
This meta Q on stackexchange.com is asking for the very thing you're inquiring about. Titled: Favorites improvements - search, categorize, personal tags, add note, favorite answer.