Create a task:
tskGlob = ["TskGlob",true,["TskGlob","TskGlob","respawn_west"],getPos player,"CREATED",5,true,true] call BIS_fnc_setTask;
Delete it:
["TskGlob",true] call BIS_fnc_deleteTask;
Check it:
player sideChat format ["%1",["TskGlob"] call BIS_fnc_taskExists];
EDIT: Do NOT test just checking the journal (key J) to see if there is task or not, as it seems the journal part is working. What is failing is the interaction between those functions (common variable use, I suppose)