The @theia/toolbar extension contributes a global toolbar to the application shell. The toolbar supplements the Command Palette and allows users to easily add, remove, and rearrange toolbar items to their liking. The toolbar is hidden by default and ships with a default layout which can be overridden by downstream applications. Extenders can also contribute custom widgets to the toolbar through a contribution point.
Additional Information
An example toolbar custom widget and layout override can be found in here.