The NetSuite user event script supports record save contexts from many use cases like field edit through UI, script, mass update, inline edit etc
The field edit context that is not supported in user event script ‘afterSubmit()’ entry point is the ‘Set Field Action’ through a scheduled workflow. To solve this, you can schedule a mass update(only for body fields) and use ‘XEDIT’ context to get the context. You can also try workflow action script from workflow