library/library_app/views/library_menu.xml

<?xml version="1.0" ?>
<odoo>
    <menuitem id="menu_library" name="Library" />
    <act_window id="action_library_book"
                name="Library Books"
                res_model="library.book"
                view_mode="tree,form"
    />
    <menuitem id="menu_library_book"
              name="Books"
              parent="menu_library"
              action="action_library_book"
    />
    <act_window id="action_library_book_report_window"
                name="Book Report"
                res_model="library.book.report"
                view_mode="tree,form"
    />
    <menuitem id="menu_library_book_report"
              name="Book Report"
              parent="menu_library"
              action="action_library_book_sql_report"
    />
</odoo>