
Is there a list of events in Business Central that can be subscribed to with an extension / AL? This only contains a very short list: https://docs.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/devenv-event-types
Specifically, I'm trying to trigger something after an item is added to a sales order or credit memo.
The standard event in your case is OnAfterValidate event of the No. Field in the Sales LIne table.
You can inspect event by using Event Recorder or Go To Definition for an object.