I'm trying to place a part that is floating above the XY plain. How do I move a stl part so that I know it's on the table?

afaik you can't with the current host.

In fact is doesn't make any sense, since you cannot print that part if it's floating...

so, what you can do is, add a thread to that part so that the software will use the end of that thread as bottom.

'sid