OK, I’ve just released a minor update to the demo with a few small changes.
I changed part duplication to behave more like it did before the builder tool overhaul, so that you don’t have to hunt around for the duplicated part, and thereby hopefully speeding up the building process.
Now, holding Left Alt + LMB duplicates the targeted part. After which, releasing Left Alt (while still holding LMB) allows the duplicated part to be dragged away for repositioning.
I also fixed a couple of bugs relating to part selection and the move manipulator.