My model is not on the drop down list in create
The list of machines is a legacy from when Carbide Create calculated feeds and speeds and limited stock size to match a machine’s working area — it no longer does these things, so it’s not really necessary.
Simply specifying “Shapeoko 3” should be fine (and matches your machine since you have a Shapeoko 3, XL size).
Glad you mentioned this. I have CC 644 and opened it and it was set to Shapeoko Pro. I have run quite a few projects and ran well. So my Shapeoko 3 XXL can compete with a Shapeoko Pro? Likely just been lucky.