Are there any accurate tutorials that can show me how to create this specifically for a custom hero? I don't even know how to create one of these at all. They used the same exact thing for Nova Covert Ops, but I can't access any of their maps through the Galaxy Editor in order to figure out what triggers they used.
Blizzard made a set of triggers available on the (Story) dependencies on HOTS and LOTV. They are mostly hardcoded to use blizz heroes, but they can be duplicated and tweaked for your needs. They are a bit finicky, as you may have noticed on CybrosX's Broods Wrath, wont always properly link the low health red flash to the hero unit and can be associated to structures being built. Look for Hero Pane stuff n the trigger libraries
Maybe this will shed some light. Look at the hero panel I have. There's no image to it, the bars are wrong, there's no number next to the image that indicates leveling up, and the color is Protoss blue.
Okay, I've just been introduced to a whole new level of weird. I create two Hero Panels, and this is what I get.