Greetings.
Watching 4.12 patch notes I have seen U4 Ability System features being implemented and announced, but other than the API link I still don’t find any “how to” doc or any example.
People is interested on such feature since 2014 (as I remember), but at that time we were informed that many changes would be still implemented/changed before it become user friendly.
Is it ready to be shown/explained to us? A twitch video or complete doc about a “how to U4 fireball” would save some lives, or at least mine one. 
Best regards and thanks for your attention.
creasso