From https://community.getbeans.io/discussion/modal-menu-full-screen/ beans-framework

modal-menu.php

add_action( 'beans_uikit_enqueue_scripts', 'example_enqueue_uikit_assets' );

function example_enqueue_uikit_assets() {

    // Enqueue extra UIkit components.
    beans_uikit_enqueue_components( array( 'modal' ) );

    // Add style.less to the compiler.
    beans_compiler_add_fragment( 'uikit', get_stylesheet_directory_uri() . '/style.less', 'less' );

}

// Modify primary menu type to stack as it would in a sidenav.
add_filter( 'beans_primary_menu_args', 'example_primary_menu_args' );

function example_primary_menu_args( $args ) {

    return array_merge( $args, array(
        'beans_type' => 'sidenav'
    ) );

}

// Add the modal menu button.
add_action( 'beans_site_branding_after_markup', 'example_modal_menu_button' );

function example_modal_menu_button() {

    ?>
    <a class="uk-float-right" href="#example-modal-menu" data-uk-modal>
        <i class="uk-icon-navicon"></i>
    </a>
    <?php

}

// Add the modal menu with an action to which the menu will be attached.
add_action( 'beans_site_after_markup', 'example_modal_menu' );

function example_modal_menu() {

    ?>
    <div id="example-modal-menu" class="uk-modal">
        <a class="uk-modal-close uk-close"></a>
        <div class="uk-modal-dialog">
            <?php do_action( 'example_modal_menu' ); ?>
        </div>
    </div>
    <?php

}

// Change the primary menu hook to the new modal hook and remove floating class.
beans_modify_action_hook( 'beans_primary_menu', 'example_modal_menu' );
beans_remove_attribute( 'beans_primary_menu', 'class', 'uk-float-right' );

// Move the primary menu offcanvas button back to the header.
beans_modify_action_hook( 'beans_primary_menu_offcanvas_button', 'beans_site_branding_after_markup' );

style.less

#example-modal-menu {
    background: #fff;

    .uk-modal-close {
        position: absolute;
        top: 80px;
        right: 70px;
    }
}