1. Please first try to find it yourself in either: Full dvar list or GSC modding codes threads in the modding section
here's your code:
you can even chose!!!
Time in seconds before showing and starting the game start timerCode:setDvar("party_pregameStartTimerLength", 1)
don't know if they fully work since I just wait the 5 seconds...
Time in seconds before a game start once enough party members are readyCode:setDvar("party_gameStartTimerLength", 1)