Hi Roy
Ok, well now I the breakpoints are invoked on the backend system using your hints and the information in RUNTIME tab using ?sap-ds-debug=true
Still no workflows in output but I will speak to our workflow expert and get the correct IDs to insert in the table you point out and ensure my workflows are "ok". So I'm probably close to getting it to work - crossed fingers 
By the way, I want to retrieve workflows from 3 different SAP systems but would like to expose all workflows in one gateway service. Can you point me towards a standard approach for that?
Br Jan