The customisable toolbar allows you to add, move and remove buttons.
Do the following steps to customise the toolbar:
Click [View] - [Customize toolbar...].
Drag and drop the button on the toolbar to add buttons or drag a button from the toolbar to remove a button.
In the view option you can select different sizes and layouts for the buttons.
Use 'Revert to default layout' to get the default buttons and view option.
Click [OK].