After a lot of testing the newest Control Rig plugin, I’ve found a problem with adding custom variables. It’s possible to make a custom variable visible, and you can find it in the Animation Blueprint for a Control Rig node instance. However, when clicking the “output” check box for the custom variable, it enables both input and output check boxes. The problem is, only the input pin is enabled on the Control Rig node in the blueprint.
It seems that custom variables can’t be enabled as output pins for the Control Rig node.