I also have this same question. There is an old response that has some code on it, but for the life of me I could not get it to work. Maybe I just don’t understand the AI Perception well enough.
Modify AIPerception Sight Range at runtime [4.7.6] - Programming & Scripting - Unreal Engine Forums
That’s the link I found that apparently solved the problem for this person. I personally couldn’t implement it, but my coding skills are still at the beginner level so I don’t really even know where you would add that to make it work.