beast, just make a profile for a game, you can enable it there. Japamd said he's getting rid of global settings on next release anyway, so it's all profiles and triggers.
I was able to stack mlaa, ultra fxaa & ultra smaa & sweetfx's smaa in borderlands 2, although it looks like crap. No jagged edges, just overdone and bordershader is too thick & text is shoddy looking.
Noticed your thread praising SMAA - yes it's the best. Now you just need Downsampling + SweetFX & RadeonPros forced HBAO. SweetFX without RadPro has SMAA injected (FXAA too if you want) + 10 other optimized shaders like Luma Sharpening, HDR, Vibrance, Dithering & Bloom
Run your game at 3860x2160 or 2730x1520 squeezed into a 1080P display and scaled with a custom SweetFX SMAA Profile using sweetfxsettings.txt (not RadPro) and it'll look amazing. You're probably going to have to use 12.11 catalyst to create a downsampled resolution & no higher than 13.3 catalyst to keep the downsampled resolution, but it's worth it. Thats how all the screenshot gurus @ guru3d forums take their precious screenshots, and if you have enough gpu it's a playable setting too.