Wanted: How to copy a sample from one remix deck to another

How do you copy one remix deck set sample (on deck C) to another slot (on deck D), without moving it out of the existing remix deck set. Mouse/keyboard only, no F1. Using my own custom mapping for playback only.

I've searched and toyed, and am pulling out what's left of my hair.

Please, help,
DJ Elvis

You have in the controller manager: remix decks/ legacy/ copy slot from slot. That command exists both for a keyboard and a controller.

Alt+click and drag the sample.