Features

• Copy the build ID or list of extensions to the clipboard using the toolbar button
• Insert the build ID or list of extensions into a textbox using the context menu
• Option to customize the Title Bar
• Available locales: Chinese (Simplified), Czech, English, Japanese, Polish, Russian, Swedish

Limitations There are a couple of known issues due to the limited WebExtensions APIs:

• The changeset cannot be retrieved
• The extension list does not include system add-ons
• The textbox inserting options don't work on some Mozilla sites (including AMO due to a security restriction) as well as with a textbox within an iframe and certain rich text editors
• Some variables are not available for the custom title template

The following features found in the original XUL-based extension are not yet implemented, and some of them may not be implemented again:

• Copy about:support to Pastebin
• Open the profile folder (Use about:support or about:profile page instead to open it)
• Open the pushlog
• Screenshot utility (Use Firefox Screenshots instead)
• Crash options
• Extension compatibility fixer
• Menu items under Tools

See https://wiki.mozilla.org/QA/Automation/Projects/Addons/NightlyTesterTools for some proposed new features, and check out the source code on GitHub!