Everything is just broken.

[randoomx8]

You probably have abandoned this tool (which is a shame), but in the case you have not, I just want to say that on 2019.2.15f1, this is completely broken.
The FloorPlanHandle will just spawn pillars everywhere and walls will sometimes just decide not to spawn. Also using the tool causes my CPU to spike to 100% usage, usually crashing the engine.

All that aside though, the very concept of this tool is deserving of merit, this is an awesome idea and I hope that someday we may see tools like this implemented into game engines.

[randoomx8]

I forgot to check closed issues and found that someone had very similar issues to mine, sadly my prefab is already set to 0,0,0 so this does not help in my case.

[BradFitz66]

Have you tried out my fork for the tool? (this seems kinda shitty, advertising my own modification of this, but this repository seems abandoned with no future updates). You can find it + a demo of it here