Hi, I hope I am in the right place to put my question..

I am developing a quadruped robot:
https://www.youtube.com/watch?v=bt_8X4lYDGY

So I am using SketchUP make 2017 + MSPhysics to test different settings of my robot and different scenarios :
https://www.youtube.com/watch?v=fBTxNx2UAT8

Just cool! but I have a little problem:
In Sketchup I am using 8 servos, 2 for each legs and I get (as you can see in the second video) 8 MSPhysics sliders to move my 8 servos.
Ok, but I would to have another slider that let me to move, for example, servos 3,4 and 5.
So I would to obtain my actual 8 sliders + 1 new sliders that move servos 3,4 and 5.
Obviously I will be able to move servo 3,4 and 5 using both the old 3,4&5 sliders and the new one slider too!
So I will obtain :
SLIDER 1 = servo 1
SLIDER 2 = servo 2
SLIDER 3 = servo 3
SLIDER 4 = servo 4
SLIDER 5 = servo 5
SLIDER 6 = servo 6
SLIDER 7 = servo 7
SLIDER 8 = servo 8
SLIDER 9 = servo 3, 4, 5

How to do that?
Thank you all in advance!