Not sure in Qlik Sense one can do AND for 2 triggers, as in another Task completed AND it is Monday.
But in your Weekly qvf load script you could exit before doing anything with something like
Let vToday = text(WeekDay(today())) ;
if vToday = 'Mon' then
trace Today is $(vToday) so continue with script ;
trace Today is $(vToday) so exit without running script;
exit script ;