Discourse’s search is one of its most awesome features. Click the search icon (or type /) and click the “options” link.
There you can see that you can add in:watching or in:tracking to any search you like.
It does not appear that you can search muted topics. (I suppose that might be useful if you want to find some topic that you muted by mistake?) If you can make a compelling use case for that, you could submit a feature request, though you can get the list of muted topics on your Preferences page.