Tab Mover

This add-on is designed to be simple, easy-to-use, and help you organize spreadsheets that include multiple tabs. Simply drag-and-drop into the order you want, and hit apply. Simple add-on, simple logo, simple user interface, and simple function.

There's really not much to it. If you want to install it for your Google Sheets, just click here, or search for it in the web store.