Hello DadInGeorgia and welcome to the forums!
Natively in the Lutron app, hardwired dimmers or switches cannot be used to control another hardwired device. Our apologies for this. What you are looking for is an if/then statement that may be achievable through integrations. We recommend looking into
IFTTT or HomeKit by utilizing a HomeHub for automations. These integrations can check for the status of the PD-5ANS where if it detects it's in the ON position, it can then turn the device controlling the undercabinet lighting ON as well.
As you may know, a standard 3-button Pico or
Pico Scene Keypad remote can be wall mounted next to the position of the PD-5ANS with our PICO-WBX-ADAPT mounting hardware. However, we can understand if this look is not desired.