You really wouldnt have to edit every single dino. but only the DinoSettings___ that the dinos refer to. Each dino does not have their own blueprint. I think there are probably like 12. 6 for Herbivores and 6 for Carnivores… And if you edit the base, you might only need to make 2 edits. It sound like you want a blueprint solution that edits affinity at run-time. Not everyone approaches things the same way but I would have (and actually have) went with the no-blueprint option as its more straight-forward in my opinion and no extra logic needed to execute at runtime.
If you don’t have a solution by tomorrow, I may be able to play around with a blueprint solution. I don’t know off the top of my head though.