Thanks for the response, Andrew. Will have to settle for HD preview and review full resolution in the render. An unfortunate concession of a laptop. Though my machine has handled 4K in every other capacity beautifully.
I purchased a Sonnet external PCIe box and a BlackMagic 4K Intensity Pro card to use with my MacBookPro. It drives the external 4K screen. Unfortunately for my complex timelines, it won’t play without some stuttering, but probably would for less complex grades. I am able to use it with my iMac Pro and it plays back in real-time.