Sadly after doing fairly extensive research on this topic it doesn't seem possible. The best I could do was to chain the most basic WatchKit haptic type (WKHapticType- I think it was Click) together to make a pattern using a loop. But this is quite low-res as you'll have 100 milliseconds between clicks. You can get a lot more control (although less intensity) on iPhone using CoreHaptics, but this is not available on Watch.

The Stanford lectures on Swift (https://www.y outube.com/watch?v=bqu6BquVi2M&list=PLpGHT1n4-mAsxuRxVPv7kj4-dQYoC3VVu) are great if you're a more video-oriented person like me!