Rigid Sets Menu

Add Selected/Remove Selected
Adds/removes the selected Rigid Body object(s) to the selected Rigid set.
Extract Selected
Like the Remove Selected option, this option removes the selected objects from the Rigid Set, but also converts them into standard regular rigid bodies (no longer contained within a set).
Note: Attributes and values set on the Rigid Set are retained on the rigid bodies.
Empty
Clears the selected Rigid set of the object(s) it contains, but leaves the set.
Delete
Removes the selected Rigid Set(s).
Set Initial State
Lets you set the initial state of a simulation to a point in after which the solve has already started. For example, walls comprised of stacked bricks might need to settled before running the main simulation. The Set Initial State setting creates a mesh copy from the selected mesh and connects it as an input the bulletRigidBodyShape node.

The initial state lets you take a "picture" of your rigid set simulation at any frame, and sets that as the first frame.

Reset Initial State
Returns the selected Rigid Set back to its original starting point at the time of creation.
Note: You must reset initial states after loading and before exporting scenes that contain rigid sets to an Alembic file.
Note: You may need to rewind to the beginning of your simulation to see the effect of this setting.
Select Initial State
Lets you select the initial state of the Rigid Body simulation so you can view it in the Attribute Editor.
Note: The initial state is an actual initial state node contained within the bullet solver.