Milkman
An extensible request/response workbench
... for request aspects (e.g. table-based editors for headers), importers, whatever it is, you can extend it. The core application only handles Workspaces with Environments, Collections, Requests, and their aspects. Several plugins are provided already that extend the core application to be a replacement for postman. Crafting and Executing Http/Rest requests with json highlighting. Support Proxy-server configuration and SSE.