Get your raid assignment when you target a unit. Write your own assignments in Actions > Init like so:
a["Anub'Rekhan'"] = "Heal the tank"
a["Kel'Thuzad"] = "Grp 2 kick"
a["NPC name"] = "Assignment"
Demo: https://www.dropbox.com/s/ekbpdkal55or3vr/2020-12-26 09-56-01.mkv?dl=0
Icons are added to the assignment based on the words on the assignment, for instance it will look for the word "kick" and give it a kick icon. Icons can be added below the assignments.