Maybe we are talking past one another. Are you speaking about this? "IK_l_arm_elbow_control". Thats only being used as a swivel goal. Which I was just trying to figure out how to turn on/off that boolean in its options through parameters. Or do you mean with IK elbow upnode, making on the slave rig thats looking 50/50…
You can use this code to place the ik elbow upnode in the right angle / spot when switching. Using to normalize part and the matrix part will give you a transform matrix. Use it to place the upnode target