As demonstrated in Cantabile Webinar 20, this uses the mod-wheel with the Routing tool’s “Conditions” section to cause the mod-wheel to let your controller play the lower manual along with unison bass pedals in slow Leslie speed at the bottom position, and play the upper manual with fast Leslie speed in both UVI’s Rotary and the organ’s built-in Leslie effect when the mod-wheel is pushed to the upper position (above 64).
Use “Replace Plugin” to adapt this to your own organs and outboard Leslie effects, or remove the outboard Leslie plugin entirely. As a template, this should prove interesting.
Here is the full rack with the organ and the external Leslie plugin (UVI’s Rotary) baked in. Use “Replace Plugin” to swap out to make your own rack versions.
Here is the simpler template that uses the output ports to send the results to your VSTs.