I had forgot that a while ago, I had to create a custom HL7 message, and I saw a question on the forum asking how you can do it.

Here are the steps: (All modifications take place in both the MSH_24_GLO_DEF and the tablevalues.xsd). In this example I am creating a ZZZ^Z01 message;

1. Edit Table76 and add the message type (add an enumeration) by editing the schema in a text editor:(in my case ZZZ)
   
2. Edit Table3 to represent the trigger:(in my case Z01)
   
3. Edit the Table354 that represents the Message_Trigger: (in my case ZZZ_Z01)
   
4. Finally create your schema with the roon node that follows the following algorithm: Body schema type = TargetNS + “#” + MSH9.1 + MSH9.2 + MSH12.1 (with dots removed) + MSH12.2 (or GLO if the value is blank) + MSH12.3 (or DEF if the value is blank), and don’t forget to make sure that the target namespace of the schema matches what you have defined in the BTAHL7 Configuration Explorer
   

And finally, here is a sample.