Yes! Yes! Success!
Brendon, I decided since your version installed successfully, "What the heck, let's just do a fresh install". While doing this I noticed in the installed programs list an entry called, IIRC, Roxio Business something or other. This had been installed in 2009(!), most likely by the previous owner - this machine is a business castoff. I uninstalled this program and my previously installed CD/DVD creator product.
After much CD drive activity and clicking through Microsoft's 'must have digitally signed certificate' notification, the fresh install completed. Removed Drag-to-Disc, restarted computer, started program and clicked on 'clean up audio' and the beautiful, desired sliders appeared. And, they are functional - at least they move up and down under my control.
I suspect the old business program was interfering somehow with CD/DVD creator but I'll probably never know. I don't care, I can now remove the clicks and pops from my LPs and that's enough.
Thanks again for your help.