Assist Mode is not designed for automatic activities, therefore it is not available in Scenario Engine.
The feature you ask about belongs to Custom fights and Monster grind feature pack. The combat system is still in early beta and there are several critical updates that must be implemented before this feature becomes possible.
In addition, Miqobot will not be able to perform dungeon mechanics until we manually implement each of them in Miqobot source code. Without additional algorithms, Miqobot will simply stand in acid puddles and AoE omens. So this feature will not allow you to farm any dungeon out of the box.
You can find more information in this thread:
Open scenario scripting engine for squadrons/combat