The Gmail UI update is a Chrome add-on developed by michelet.tristan. It is a free program that falls under the category of Browsers and the subcategory of Add-ons & Tools. This add-on aims to fix a couple of issues related to the action bar when using the multiple inboxes Gmail lab plugin.

One of the problems addressed by this add-on is the inaccessibility of the action bar when using the multiple inboxes plugin. With this update, the action bar is now conveniently moved to the top or bottom of the Gmail interface, ensuring that it is always reachable regardless of the user's configuration.

For users who rely on the multiple inboxes plugin for better organization and productivity, the Gmail UI update provides a simple and effective solution to improve the accessibility and usability of the action bar.