Ok.
In my latest build, I added support for variables in feedback. They can either be used in place of a value, or unique to this build, they can also be set.
When using them to “get” (retrieve) a variable value use the normal $ sign as in $(internal:custom_Ch1_Fader)
When using them to “set” (store) a value into a variable, use the @ symbol as in @(internal:custom_Ch1_Fader)
Here’s a demo of a simple use for checking the value of a fader: