Quick question (hopefully) about a robotics Servo option

[Inter]

Hi, folks. 
I was watching a video recently where I saw the host using an option in Action Groups to set a setting called "Toggle Servo" for the Rotation Servo M-06.  (In case you're wondering, that part is the smallest servo and the one first acquired in the science tech tree, but I suspect this setting option would be available for all of the other servos as well.)  His screen looked like this:
https://imgur.com/jrOChjN

However, when I click on the same part in my own KSP, I only see the following two options.  There is no "Toggle Servo" setting available to me under Action Groups > Custom#.
https://imgur.com/fHdofhD

Does anyone know how the "Toggle Servo" option is acquired?  Yes, I have already reached out to the video owner but the mystery persists at the moment and I'm hoping to have this solved by EOB today. 
Thank you.

Also, since I'm new to posting pictures in this forum, I'd be tickled if anyone could apprise me of how to make images appear as embedded thumbnails instead of mere links.  Cheers.

[Geonovast]

You might need to turn on Advanced Tweakables in your game settings.

[Snark]

Moving to Gameplay Questions.

2 hours ago, Inter said:

Does anyone know how the "Toggle Servo" option is acquired?

It's only present when "Allow Full Rotation" is set to "disabled" on the rotational servo.  Since it's enabled by default, that's why you're not seeing it.

[Inter]

50 minutes ago, Snark said:

It's only present when "Allow Full Rotation" is set to "disabled" on the rotational servo.  Since it's enabled by default, that's why you're not seeing it.

I apologize if I'm quoting you unnecessarily.  I don't know how to reply directly to a person in this forum.  Thank you for the answer, that was what I needed!