Hi,
Sorry if I don’t know the exact name of this but I just opened the free rig from animation mentor and it has this drop down attribute in IK to FK and FK to IK that executes automatically.
Please see illustration here: https://www.dropbox.com/s/g3fo88mnjhg1fji/MYA067_ikFKSnap_dropDown.mp4?dl=0
Is there a reference out there that can do this?
Thank you.