This might not be my place to say but when it comes to CC, which i think you mean is “Crowd Control”. There must be a visual representation and a clear intent of what it would do.
Example: Damaging abilties being Clear and Sharp, Healing abilities being vague and soft. CC would fall into that catigory. How the priority would work idk. But visual representation is always key.
If you debunk Lissandras W. The visual representation is that the ground becomes frosted with the intent to “freeze” a Champions feet to the floor for a certain duration!
Same with her R. There is a clear visual representation of someone being encased in ice, and being unable to move until it fades away.
Another one is Leona from LoL. Whilst her Q and E are fairly simple (she was made a real while ago so understandable) Whilst her R is a sunray binding the opponent in blinding light. Or you have Ahri with her charm, the charm wouldnt have the same impact if it was just a sphere or any random shape, the “heart” combined with the soft particles and charmy / romantic color, gives the hint that the enemy truly will be charmed by her.
TL;DR Whats hard about visual representation is to get across the Intent and visual representation without cluddering, aka You want a heal effect to be looked on as a heal by major majority, and a damaging ability to be looked on as damage by the major majority.
Please correct me if im wrong, this is just my take on it.
Idk if that was to any help.