This is an older post but I was looking up how to draw a debug line and visually be able to see it while debugging and this is one of the first things that pop up in a google search. I just wanted to take a quick moment to update this question in case there are other users looking for the same thing.
while using c++ you can draw a debug line in Unreal by using the DrawDebugLine as follows:
DrawDebugPoint(
GetWorld(),
Location,
20, //size
FColor(255,0,255), //pink
false, //persistent (never goes away)
0.03 //point leaves a trail on moving object
);
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