ArcGIS Web Appbuilder editor widget with limitations on which users can access the tool in a given application.
If anyone plans on implementing this, go into the setting/Setting.js file and update the line below the TODO with your Portal URL, as well as an email address or other POC in the else clause in onOpen in the Widget.js file. Applications built with this need to be housed on another web server accessible to your users, and a link to that server needs to be created as an item in your Portal.