I cannot get the fc_Predefined:EmailSender (or another Email registration parameter) when I try to call them as a registration parameter in my scripts. What code should I use?
The fc_Predefined:EmailSender parameter, as well as other email-related parameters, are available on the batch level, not on the document level.
So if you need to call it in scripts, use it as string value with the code like this:
FCTools.ShowMessage("Email from " + Document.Batch.Properties.Get("fc_Predefined:EmailSender"));