I mught very well be dumb or too tired toifind it but I can't find the number successes needed to do complex manipulations in the scenarios.
This is completely dependent on the scenario/manipulation, but if there is no number of successes listed,
then you just need 1 success (e.g. the chests in most scenarios). Correction: page 9 of the Heroes' book says, under the topic Opening a Chest: "The difficulty of the Manipulation is 2 unless the scenario specifies otherwise."