Customizing Nuke with Gizmos - Nuke 101: Professional Compositing and Visual Effects - page 528

17. Click OK.
You want this Knob to be the bottom one in the interface.
18. With your new Knob selected in the list, press the Down button three times, then
click Done to close the User Knob panel ( FIGURE 12.47 ) .
Figure 12.47. A new check box appears.
For now, this new Check Box Knob does nothing. You'll link it to an expression.
19. You should already have the Properties panel loaded for Switch1 and Group1. If
you don't, please load it now.
20. Ctrl/Cmd-click and drag from the actual check box you created to Switch1's
Which property's Input field ( FIGURE 12.48 ) .