It seems as though this has stopped working. I just see "if(YourDim=YourDim,YourDim)" in the filter bar now. Is there a solution that still works?
Edit: Actually, it does work...sometimes. It wasn't working for me, but when I created a second dimension with the same exact formula, it worked for both that dimension and the first one. Oh, how I love Qlik's missing basic features and associated buggy workarounds.