I am trying to get a better understanding about Rigid Bodies and simulation setups, hence this quick question.
I want to manually control the Center of Mass on my RBD object. Is this position measured in the object's local space or in world space?
I assume this parameter serves to initialize the CoM on the first frame of the simulation and then follows the object during it.

It's the initial world space position of the center of mass.

cwhite
It's the initial world space position of the center of mass.

Trying to fully get this center of mass thing, I tried defining a pivot attribute before going into RBD solver but that didn't seem to work. So how do I really go about setting the COM manually using an attribute?

The default behaviour is to compute the COM on the first simulation frame, so you probably need to turn off Compute Center of Mass (the 'computecom' point attribute)