All non-rookie users use difficulty comparison to speed up their CH's by planning the most difficult things first.

Build a clear interface to visually create a difficulty comparison.
For example: In course scheduling, compare the difficulty of the Lectures by first comparing course size, then student size, then teacher load, etc.

I imagine the interface would look like Excell's interface when sorting rows based on the value of multiple columns.

Then allow it to be annotated on the domain model, like in PLANNER-325.

http://docs.jboss.org/optaplanner/release/latest/optaplanner-docs/html_single/index.html#planningEntityDifficulty
http://docs.jboss.org/optaplanner/release/latest/optaplanner-docs/html_single/index.html#planningValueStrength