OK I don’t know if others know this, knew this, or what, but I just discovered it. For the longest time when I moved an object, it would always return it to it’s Z position. If I wanted to raise it to add something under it, it would return to the plate. Tonight I have this HUGE part I am printing that it failed due to the support breaking. Didn’t come off the plate, it snapped about 15 MM above the plate, So, instead of starting a 300 x 200 x 180mm part all over again, I measured the part that did print, and slapped a negative part to not print up to what still needed printing. Sliced it and of course wanted to print supports up to the part where I want the actual part. So in playing around, I inadvertently flipped to world coordinates on the part, and it stayed put. I then hanged the Z to the point I want to print and sonofagun, it sliced starting at that point and is actually printing only what I want! So you CAN move the part below the Z center! Oh thats going to help me out a LOT! I will just glue the two parts together.
Why not just cut it?
Yeah, this has been around for a long time.
It would be far more obvious if users could have the z-axis value start at zero at the build plate and not 50% of the single object or combined merged objects.
I use thus a lot to test shapes in models.
For example I designed an interlocking box almost the size of the build plate, I need the plug and socket sides to test. Printing almost a kg of material to confirm it works isn’t sensible. I could Boolean the bottom parts of each side in the model. But, that is destructive and it is easier to set the z axis of the model to below the plate.
The slicer only slices the portion still peeking above the build plate.
Yeah, thats what I discovered tonight. I normally use Tinkercad to cut up my parts as it only takes about a minute or two to copy the part, block out what I don’t want and download whats left. In this case it was due to the printer breaking he support and I really didn’t want to waste a half days work and a half spool of filament so stumbled upon it by accident. Last time I tried to move the part it kept bouncing back to the plate so never really figured it out until now.
Worked good. Not perfect, but then again neither is the full print, still some support and banding issues due to it being so big. I also should probably run a calibration on it, haven’t do9ne one in a while. Was able to glue the printed part onto the part where I stopped the print and everything mostly lined up. It’s the back half anyway and really can’t be seen. It’s a POC anyway and POC passed.
but what about the split tool? 
in bambustudio, you get extra option like dowels etc