public final void showNavigationDrawer() {
        showDrawer(navigationDrawer.get(), Side.LEFT);
    }
Hides the currently displayed drawer that was previously shown using
{@link #showDrawer(Region, Side)} or {@link #showDrawer(Region, Side, int)}.
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/Workbench.java