Windows 11
V. 3.1
I can save a 6 second preset for silence on one end of the wave but I can’t seem to save it for both ends at the same time.

I think you need to make a macro for that …

If the track isn’t too long, you can add 6 seconds to the start and end using this code in the Nyquist Prompt effect (

(defun add-space (sig current added)
    (sim (s-rest (+ current (* 2 added)))
         (at added (cue sig)))))

(multichan-expand #'add-space *track* (get-duration 1) 6.0)