Seconded. Support rebel is probably the only mission that I really like, but the lack of knowledge of how effective it is deters me since revolt risk is gone (earlier, I felt the UI was much better; I knew I would increase RR by that much, while now, I just don't know what 0.04% is; it's tiny and looks terribly useless). I also can't know when rebels will pop up; it's not that I want to support every rebelion just 1 week before it pops, but some are just bound to never pop because unrest decreases over time, or literraly take decades (esp. if the AI has increased stab or taken the -unrest advisor in the mean time) before anything good happens while I'll bleed money for it.
Last, and that one isn't UI oriented, being discovered should do something more. When I'm discovered, I often just send my diplomat ASAP, even if I'm doing it for the 5th time. It does nothing for the one protecting against rebel, and it does nothing to me out of annoying me and making me click a couple times more.