Not sure if this is exactly what you’re looking for, but UE4 uses 1 UU= 1 CM. So setting your scale inside your modelling tool of choice should help you out with that aspect. If what you actually mean, is the ratio of your created objects to character size, I recommend getting a known object size (i.e. import a basic human model) and use that as your reference for creation. Alternately, you can do it the mathematical way, and measure everything
Edit:
Nevermind.
Man, I’m 0 for 2 today. That’s what I get for posting soon after waking up and not completely reading.