Windows 7 x64, GTX790
Blender 2.78 from builder.blender. org. Date 2017-06-06 - 10:14. Hash 58a434b
Short description of error
This already was reported by Me a while ago, then fixed, and now it occurs. It's something fresh, because not that while ago ( maybe a week ago) it was working.
I'm always using builds from builder. blender. org.
Rigify rig, keys for IK/FK sliders aren't shown in Action Editor, Dope Sheet or Graph Editor. There is an indicator in Dope Sheet, but key is only visible as there is a key in scene, but the property of that key isn't there. You can do nothing with it. This is very annoying, because it was fixed, and now the same issue. You can't work on animations without knowing where the keys are, especially when shifting from FK to IK in one take.
Exact steps for others to reproduce the error
Add rigify (legacy, not new with face controls), add a key to FK/IK slider for example on hands. And take a look on DopeSheet, ActionEditor etc.