Between March and May 2016 a group of students at Harvard University created a web-editor for HELM as a project assignment for their course. The report, a demo version and links to the code are all below.
Link to page containing demo version
http://104.236.250.11/editor/dist/#/
Code repository
https://github.com/CSCIE-599/HELM-Editor-UI
Report on the HELM Editor project