I think that pretty start menu lures a few newbies into the hard-to-escape editor, from which many probably alt+f4.
I suggest to add an X button where you would expect, basically emulating a safe Ctrl+Shift+E
!image
It's not the prettiest, but the space is pretty narrow, all-round doesn't look so good either:
 server is full (2) server is empty (3) player slots are full
<Dune> right now, there is (1). this would add (2)
Right now the code uses
float SpacingW = 3.0f;
float ButtonWidth = (Status.w/6.0f)-(SpacingW*5.0)/6.0f;
...
Label.VSplitRight(ButtonWidth*2.0f+SpacingH, &Label, &EditBox);
so gotta find an elegant solution