Views:
Question:
Is it possible for Global Variables to be used within the JSON when setting up a Web Service Activity?

Answer:
By product design, using Global Variables within the JSON path would not be possible.

KBA applicable for both Cloud and On-premise Organizations 
This article is valid for DocuWare versions: 7.5, 7.6, 7.7, 7.8 7.9 | Workflow, Web Service, JSON