Hi @kenw232 - welcome to the community.

As I understand it, at the moment, Klaviyo Webhook Actions can be user defined and arbitrarily added to any place within your Flows.  Since Flows can be triggered from a number of ways (See Flow Trigger explanation) and have any sequence of conditional branches, there isn’t a finite list of Webhooks since in theory you can have an unlimited number of Webhooks.  

For example, you can build a Segment Triggered Flow, for anyone that’s Placed an Order 3 times in the Last 6 Months to send them a “Thank You Email” - you can also send a webhook specific to this Flow.  You can see, those are arbitrary parameters, you could have easily changed it to Placed Order 5 times, and changed the time to 12 months.  Since you can create Segments however you define, you can have unlimited “Flows” for each of those Segments to trigger a Flow.  

Hope that explains it!

By the way, if you’re a developer, join us in the Developer Group here in Klaviyo!