Thanks for working on this, Mitchell. Found a couple of bugs:
Click on a subforum such as ST 2.x Q&A. Click on the forum search and type in a term and hit enter. On the results page, click in the box and hit enter again. It will change your forums to add all the ones you had in the filter popup the last time it came up. The same is true if you click add/edit forums and click to dismiss the popup without changing anything.