User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-4813670-20131015130755/@comment-17735225-20131015133221

As the custom quests are saved into the save file, editor would basically act like custom quest maker, which is considerably easy to work with, just change the value of which monsters to appear, place they spawn in, monster AI value (They probably used the value for monsters freezing at first time encounter, before the cutscene).

The more challenging / requiring more knowledge / very risky ones would be to directly alter the stats of the weapon/armor/charms. This is probably the one that might break the copy and the reason why people choose to just farm those lvl 100 quests.