If you have a skelatal mesh selected thats not the original skel mesh that created the you cant select the tab. I ve noticed this seems to be isolated to .14 I tried on .12 and it worked fine
In addition to this if you select an anim it always shows the original mesh unless you select a different one from the scene setup opposed to the drop down list of meshes like you could in previous versions. currently if you select an anim after a you choose a different mesh it forces back to the original.
I can make a video demonstrated if needed. For testing I imported the same mesh under different names so the skel is with out a doubt identical