I want to know the naming convention used by mgear.
Are there any related documents or explanations?
I hope I can see the roles of cns, npo, cnx, etc.
I am afraid it is not documented. Also not 100% strict 
cns = Constraint (usually input a constraint or prepare for that task)
npo = Neutral pose (This comes from Softimage terminology)
cnx = Connexion
lvl = Level. Just another transform/group level
I don’t recall all. But feel free to ask
thanks!
npo, cnx, lvl understood!
However, the only node connected to the cns(e.g. global_C0_ik_cns) is the dagpose.
Does it just indicate that the constraint is on the controller below?
The default global_c0 component is of type control_01. This type of component always creates a ik_cns group for the IK space switching functionality. If you go to the component settings you can see that it has an IK reference array available. But this is left empty by default, so the global_c0_ik_cns group is left unconnected when the rig is built.
Thank you!
I need to see the code for a more accurate part, but I know what it feels like.