This is excellent solution for making mission for MP from thread Dedicated Server - text broadcast to all?.
Shk made a comment and I am quoting him here with some remarks and highlights:
Triggers are local to each machine. All text display commands are local as well.
The secret to MP editing is command called publicVariable.
Here is a generic example of ato make sure something gets triggered/ran on everyone:
Trigger 1 Condition: !alive dude onAct: obj1 = true; publicvariable "obj1"
Trigger 2 Condition: obj1 onAct: task1 settaskstate "succeeded"
The basic idea is to have a trigger with the condition to suit whatever you are trying to wait for. Once that trigger is fired on any machines,
Trigger 2 is used to catch the true variable sent from someone.. , set taskstate, display text, end mission.
Another example, for the intel search. This covers only case where you put an area trigger over the intel and wait for a player to just come close enough.
Trigger 1 Condition: this (set trigger side/area etc normally) onAct: intelFound = true; publicvariable "intelFound"
Trigger 2 Condition: intelFound onAct: taskIntel settaskstate "succeeded"; hint "Intel was found, yay!";