Call up “All 9 Bars!”
We assume you want to control Rotary Speaker Speed
If you are doing original programming you can just make the assignment, when you are not the original programmer (as here) the wise user will study what is already assigned to control Rotary Speaker Speed Control and what else is already assigned to the Super Knob. Because otherwise you are just running with scissors down the hallway in the dark.

We recommend exploring as follows:
Go to the OVERVIEW screen [SHIFT] + [HOME] from here you can view what is happening and you can quickly navigate to view the assignments.

This Performance is two Parts. Part1 is the first eight draw bars, and Part 2 is the 1’ doing percussion, etc...
Change the OVERVIEW to view PART 1
Touch the shortcut box “Edit Part 1 Control Settings” you will be taken directly to the Control Assign screen.

Set the “Display Filter” = All
You are looking for two things: A Destination that includes the “Speed Control”, and what else is going to change when you turn the Super Knob.
Activate “Auto Select” (green) and turn the Super Knob.

Doing this you will learn that “Speed Control” is already assigned to the MOD WHEEL
And the Super Knob is also controlling some overdrive type effect ...

You can reprogram or Delete any Control Set by recalling the Destination and then touching the “Delete” box.

If it is fine with you to keep the previous programming you can proceed, but at least now you know what you are doing.

To assign Super Knob:
Navigate to the Speed Control parameter...
Press [EDIT]
Press [PART SELECT 1]
Lower left of the screen Part 1-Common in blue
Touch “Effect” > “Routing”
Rotary Speaker is INSERT “A”
Touch “Ins A”
Move cursor to highlight the “Speed” parameter set to “Slow”
The [CONTROL ASSIGN] button glows indicating this parameter can be assigned a physical control
Press [CONTROL ASSIGN]
Turn the Super Knob
You have made the assignment and are taken directly to this new Control Set screen.

You have assigned Speed Control to the position of the Super Knob. Initially all values 0-63 are Slow, all values 64-127 are Fast.
The transition speed from slow-to-fast and fast-to-slow is programmed within the Effect.

Google search for:

site:yamahasynth.com "rotating speaker" "super knob"

for me brings up as the 5th link:

https://www.yamahasynth.com/forum/3-questions-aftertouch,-output-routing,-leslie-speed-control

which covers the destination for rotating speaker speed. The context is not exactly superknob (different modulation sources) -- but the destination is mainly what the key is here.

First Thanks to Bad MR. And Jason!!!

So followed instructions to the letter.
I did get the Rotating speaker speed assigned to the SN.
BUT.....
It is Inverse.
IE: SN at Lowest setting to the left = Leslie at Highest speed .(No matter The Position of SN when Set.)
Increase the SN and Leslie Slows down in speed.(Speed Preset is set to Basic. Although I tried Fast first too)
Now I have gone thru this 5 Times. And Can not Get it to act Like the Mod Wheel functions.

It is True. I do not spend much time 'Under the hood' of the Montage. That is Why I bought so many Libraries.
I write Music. I do not Create Sounds. So I have a Much harder time at diving in. Like my friends do.

The direction of rotation and its affect on the parameter can be changed in a number of places. Although you can change the curve (the very end of the chain) - this is more difficult since the mod control curves do not include a "backwards ramp". You have to create one using user curves. So we'll take that option off the table even though it's possible.

An easier option is to change the common level assignable knob limits.

1) Push [PERFORMANCE] (HOME)
2) Use Touchscreen (TS): Press "Motion Control" tab on left-hand side of screen, this will display a new column (2nd right-most)
3) TS: Press "Super Knob" tab
4) You need to know which assignable knob is the one routed to the rotating speaker speed. Here on this screen you see 8 knobs with values on the top in green and values on the bottom in blue. To change the direction of rotation, write down the top number for that knob and write down the bottom number. Then change the top to the bottom number value and bottom number to the top value ("flip" the values). Now your assignable knob will rotate in the opposite direction as before when you rotate the superknob.

Since automatic assignment "hides" the details - you need to double-back and get familiar with what the automatic assignment did:

1) Association between superknob and common-level assignable knob (in other words, which common assignable knob number)
2) Association between common-level assignable knob and PART-level assignable knob (in other words, which PART assignable knob number)
3) Association between PART-level assignable knob and final destination parameter. In this case, rotating speaker speed.

You would work your way backwards from the PART with the rotating speaker effect's Mod/Control screen and answer #3 first.

The new firmware more easily tells you the superknob routing.