They just keep coming to me, but I thought about this the other night in the Sunday scenario.
In my opinion, and one I had expressed to HT at one time, I would just simplify everything and just get it on one scrollable tab.
Nuke these:
WW1: WF (It was an interesting tech demo that has served it's purpose.)
Axis vs Allies (Come on guys. Lets admit it. It no longer serves any real purpose, certainly not the one it was created for.)
Steal the Sheep. This can be run in one of the Special Events arena as a perpetual placeholder event when nothing else needs to run.
Mission tab. No one has ever gone in there that I have seen and most of those mission are completely broken which if anyone went in there you would have realized.
All (If you get everything on one tab this is no longer meaningful.)
Move the Special events 1&2 to the front and show the running event name as Slayer suggests.
Move the "Player" tab listing to the front tab and rename it "Player Custom Arenas".
Getting everything on the front tab will streamline and simplify the UI and increase discoverability of what's left.
If it's not on the front tab, it is invisible to 99.999999865% of players.
$0.02