Quick Audition Question

I am trying to add a sustain to the end of music that I cut short in Audition. I’ve seen Mike do this many times during FJF, but I’m blanking on it! I thought it was an envelope that you set points for but I can only see the volume and pan envelopes!

It’s been a few years since I did this, anyone know how to add that sustain at the end of a track?
Thanks!
Rob