What it Is
The ToolBar is a graphical extension of the Menu and provides convenient access to a small set of common actions.
How Does it Look/Behave
The ToolBar is located toward the top of the main application window. On operating systems where the Menu is also part of the main window, the ToolBar is immediately below the Menu. It contains buttons with graphics and no labels. Descriptive texts show on mouse over. Buttons change availability based on the current selection or some internal state of the application. For instance, the Delete button is unavailable when an irremovable element is selected (such as the score node).
What to Use it For
You use the Toolbar whenever convenient, or to trigger actions not exposed by the rest of the UI. For instance, use the ToolBar to start/stop score playback.
Note: the complete list of pending bugs, features and epics is available in Jira.