Congrats Dijker!
@homeyuser have a look at the flow viewer @Erik made: https://github.com/irritanterik/homey-realtime-logpage/blob/master/flowview.html
Think you can find a lot of API endpoints in it (Not sure if adding is one of it though)
You can find some more information about it here:
[HOW TO] View your Homey v2 flows in a browser
(This was posted after Homey V2 was released and Athom still believed in the Mobile only strategy, it’s superseded now by flow.homey.app)
btw, I think you’d want to use POST to create.