Extend Panel Menu

The panel menu GNOME Shell deserves.

GitHub

Extend Panel Menu is an actively-developed fork of Julio Galvan's original incarnation, featuring support for the latest versions of GNOME shell and a modern build system.

Nocturnal

Toggle between day and night with ease.

GitHub

Nocturnal is a GNOME Shell extension that allows the user to toggle their GNOME Shell and Gtk themes between a light and dark theme with the press of a button.

Spruce

Arrange windows from the comfort of your keyboard.

GitHub

Spruce is a GNOME Shell extension that extends the built-in window snapping features to provide tiling window-manager-like capability to GNOME Shell, and is heavily inspired by the macOS app Spectacle.

Duplicate Tab

It does (almost) exactly what you would think.

GitHub

Duplicate Tab was a macOS Safari extension that provided the incongruosuly-missing feature duplicating the current tab (including attributes of the page's state, such as the scroll position). It is no longer actively developed unfortunately (it is missing some important features due to API limitations), and the author has since migrated to FireFox.