You need to set which properties are special if you want to change your icon appearance if:
- Level is locked
- Level is completed
- If you want to display the level number
That’s an easy thing to do. First you have to create new property. For the locked and completed it can be any type, but the level number must be Text. Then you have to choose this property from the list in the Special Properties section.
You can read more about this here.