Hi, Ben,
Thanks for the quick reply.
Adjusting the DC offset correction would do it -- that didn't occur to me! --, although it's not as easy or as obvious as simply grabbing the waveform with the mouse and moving it up or down.
I do have licenses for the older Signal Scope and Signal Suite. I figured it was time to upgrade.
While we're at it, the documentation for X always refers to iOS/iPadOS pinch-to-zoom and other touch gestures. I'm on a Mac, so it took a bit of hunting to find the keystrokes and such to make those same visual changes.