Hold down keys when clicking the mission to customize.

Space Bar: Re-roll ships.
Control: Reset settings.

M Key: Toggle mission goal.
D Key: Next player faction.
F Key: Next enemy faction.
A/S Key: Decrease/Increase battle size.
E/R Key: Decrease/Increase enemy advantage factor.
I/O Key: Decrease/Increase player quality factor.
K/L Key: Decrease/Increase enemy quality factor.
Y/U Key: Decrease/Increase player ordnance points bonus.
H/J Key: Decrease/Increase enemy ordnance points bonus.
[ Key: Cycle player s-mods.
] Key: Cycle enemy s-mods.

Q/W Key: Decrease/Increase objective count.
Z/X Key: Decrease/Increase map width.
C/V Key: Decrease/Increase map height.
T Key: Toggle time acceleration.
` Key: Toggle "crappy autofit".