Try (modetexlist $gamemode $mutators 1)
to start with the mode. The default seems fine to me, as I noted, just like replacing the mode icon with the gsm (if there is only one
There is also a fourth arg, but i don't think it has any effect on this. Just tried different $x with (modetexlist 4 (<< 3 14) 0 $x), quick-king-defend, and did not notice any difference.
EDIT: So, using a 1 for the last argument will add implied muts to the list, like FFA for editing.