To move a call in progress to another device, press the button under More until you see an option for Park, then press the button under Park.
When you park the call, the phone will read outloud an auto-generated pickup code, like *806. It will read the pickup code at least three times.
"Your call is on hold at the following parked number: *806."
You can put the handset back on the hook once you've memorized the pickup code.
Once you know your pickup code, go to your new device, like the Zoom app on your cell phone or on your computer, then dial the pickup code, including the star. The caller will be taken off of hold automatically and reconnected.