I'm trying to implement this:
"You can use miles to island-hop. United charges 5,000 for a one-way flight on Hawaiian or IslandAir. They even allow a free stopover on a round-trip so you can fly Oahu-Kauai-Maui-Oahu for just 10,000 miles."
I've tried to search a multi-destination on united.com going HNL-LIH-OGG-HNL. It lets me select the first flight from HNL-LIH, and then once I get to the second flight from LIH-OGG it won't let me select either flight. When I check that separately as a one-way it does allow me to purchase those same flights for 6k miles.