Yes, exactly - I want some kind of idiot-proof drop down allowing me to populate variable values in the object properties using constants I've defined. I think in Unity such drop-downs are accomplished with enums, for example, but it's been awhile.
I can see how your suggestion for setting variables using event sheet logic works for objects that all need to be initialized the same way - I am actually doing that in one case. But I'm referring to a bunch of object instances of the same type that need to be initialized with different values at design time. Another hypothetical example that's hopefully clearer:
I have a bunch of doors in a building layout, and I want some of them to start locked, others to be open, others to be closed, and they are all based on a single "Door" object. I implement their open/locked/closed states by giving the Door object a string variable called "State", and using "open", "locked", "closed" strings as my state values. In my layout I then select the doors one by one and type whatever state I want into each of them. If I could set those variables using string constants (instead of repeatedly hand-typing them), they'd be less error-prone and easier to rename/refactor later on. Basically the exact same reason constants are used in event sheets, but applied to object properties at design time.
Anyway this is a pipe dream for now, unless there's a really elegant workaround I'm overlooking.