wordpress seo yoast change xml sitemap priority for taxonomy

Question

I'm using the WordPress SEO Yoast plugin on a website. In the XML sitemap settings, I enabled the Yoast plugin sitemap and it is working fine. In the admin panel, there is the taxonomy named "stores". This is like categories. But I need to set its priority from 20% to 60% in the store-sitemap.xml file.

I added the following filter and it is not working and not displaying to set the priority when adding or editing the stores.

add_filter( 'wpseo_metabox_prio', 'move_yoast_metabox_down' );

function move_yoast_metabox_down( $priority ) {
    return 'high';
}

But this priority setting option can be viewed in the post types. 

Can anyone give me a solution?