Not sure if this has been posted yet, but if it has, here is a refresher.
Go into your mq2map.ini file, change the bottom section to
[Left Click]
KeyCombo1=/dgexe melee /multiline ; /nav locyx %y %x |log=off
KeyCombo2=/dgzaexe /multiline ; /nav locyx %y %x |log=off
KeyCombo3=/dgexe caster...