In BizTalk one could use logical functoids, set it to a true value, and then attach it to an element in the destination schema. This would have created an empty node in the transformed message. This behavior is not there in the map available with Service Bus EAI and EDI Labs.
There can be different workarounds to create empty nodes with the mapper available with Service Bus EAI and EDI Labs. You could use map operations like MapEach to generate empty nodes but the best solution would be to do this:
1. At the top of the Map designer surface click Settings
2. In the Configure Transform Runtime dialog box, on the Null/Empty Data Handling tab, select Generate Empty Nodes. This should generate empty nodes for you in the transformed message.