I faced the same issue and finally got the answer:
For functions.php
:
register_nav_menu( 'primary', __( 'Navigation Menu', 'Removemymug_Theme' ) );
register_nav_menu( 'second-menu', __( 'Second Menu', 'Removemymug_Theme' ) );
For Secondary Menu (Footer):
wp_nav_menu( array(
'menu' => 'second-menu',
'theme_location' => 'second-menu',
'depth' => 2,
'container' => 'div',
'container_class' => 'navbar-collapse collapse',
'menu_class' => 'nav navbar-nav navbar-right',
'fallback_cb' => 'wp_bootstrap_navwalker::fallback',
'walker' => new wp_bootstrap_navwalker()
) );
For Top Navigation:
wp_nav_menu( array(
'menu' => 'primary',
'theme_location' => 'primary',
'depth' => 2,
'container' => 'div',
'container_class' => 'navbar-collapse collapse',
'menu_class' => 'nav navbar-nav navbar-right',
'fallback_cb' => 'wp_bootstrap_navwalker::fallback',
'walker' => new wp_bootstrap_navwalker()
) );