Feature req: Expose WebExtension entry point to trigger Zen’s floating URL bar/new-tab workflow

[rodalpho]

I would like to use a Gesturefy gesture to open the URLbar the same as Ctrl-T, but it seems this is not possible.

Please excuse the obvious AI-sourced request below, I hope the additional detail is helpful. Was playing around with the new gpt-5-codex model and had it analyze the source to confirm this was in fact not possible without code changes.

Zen replaces Firefox’s default Ctrl+T path with a floating omnibox overlay, implemented in chrome-only code
(gZenUIManager.handleNewTab). That path is currently inaccessible to WebExtensions. The request is to expose
a documented and supported mechanism (WebExtension API, command, or message) that lets extensions invoke the
floating new-tab experience without creating a real tab first.

Background / Motivation

• Gesture-based extensions (e.g. Gesturefy) want to offer “New Tab” gestures that match the stock Ctrl+T
  behaviour in Zen.
• The standard WebExtension API browser.tabs.create skips Zen’s override and opens a regular tab.
• Gesturefy’s custom scripts execute in content scope; they cannot call chrome globals such as
  gZenUIManager, send internal commands (Browser:OpenLocation), or flag the URL bar with zen-newtab.
• As a result, gestures can only approximate Zen’s new-tab flow by opening tabs, which breaks the floating
  overlay experience that differentiates Zen.

Current behaviour

1. Press Ctrl+T → BrowserCommands.openNewTabOrWindow → gZenUIManager.handleNewTab → floating overlay appears
   with no new tab created.
2. Call the WebExtension API browser.tabs.create({active:true}) (either directly or via Gesturefy) → a
   standard tab is created; no floating overlay is shown.
3. Gesturefy custom scripts (running in page scope) cannot reach window.top.gZenUIManager, call
   goDoCommand("Browser:OpenLocation"), or synthesize the required chrome attributes (zen-newtab, zen-floating-
   urlbar).
4. There is no documented experiment API or browser.zen.* namespace for this capability.

Requested solution
Provide an officially supported way for WebExtensions to trigger the same code path that Ctrl+T uses,
without requiring source modifications. Possible implementations (any one would solve the problem):

• Expose a command or WebExtension API, e.g. browser.zen.urlbar.openFloating()
  or browser.commands.execute("zen-open-floating-urlbar"), that internally calls
  gZenUIManager.handleNewTab(false, false, "tab", true) (or equivalent) and mirrors the attribute/cleanup
  behaviour.
• Alternatively, register a runtime message listener (e.g. on a new browser.zen.* API or an allowed
  runtime.sendMessage({type:"zen-open-floating-urlbar"})) that forwards to the same logic.
• Document any required permissions or user prompts if applicable.

Key requirements:

• Invoking the entry point should display the floating omnibox overlay exactly as Ctrl+T does.
• It should not depend on the current tab being empty, and it should reuse the existing close/cleanup path
  (gZenUIManager.handleUrlbarClose).
• The API should be available to signed WebExtensions so that Gesturefy (and similar tools) can bind
  gestures to it.

Use cases

• Gesturefy: map a mouse gesture to the floating new-tab overlay.
• Keyboard or automation extensions: invoke Zen’s overlay via custom shortcuts without simulating Ctrl+T.
• Accessibility tools: provide alternative triggers for the omnibox without manipulating browser chrome.

Benefits

• Preserves Zen’s UX consistency when users adopt gesture/automation extensions.
• Offers a future-proof, documented hook instead of relying on unsupported chrome internals.
• Enables broader ecosystem integration (macros, accessibility utilities, etc.) with Zen’s flagship feature.

Additional context
Relevant code paths

• src/browser/base/content/browser-commands-js.patch:9 – Ctrl+T handoff to gZenUIManager.handleNewTab.
• src/zen/common/ZenUIManager.mjs:280-360 – Floating overlay setup/teardown.
• src/browser/components/urlbar/UrlbarInput-sys-mjs.patch – Behaviour gated on the zen-newtab attribute.
• Gesturefy’s user-script runner (Gesturefy/src/core/helpers/user-script-runner.mjs) illustrates the sandbox
  and why chrome globals are unreachable from extensions.

Thanks for considering making this workflow accessible to WebExtensions!