Want to show on specific Taxnomy

Hi.

You mean you want to use this plugin with only one of your taxonomies?
Plugin home page, first snippet:

add_filter( 'sftth_taxonomies', 'my_taxonomies_with_thumbnail' );

function my_taxonomies_with_thumbnail( $taxonomies ) {
    unset( $taxonomies['post_tag'] );
    $taxonomies['my_custom_tax'] = 'my_custom_tax';
    return $taxonomies;
}

Or shorter in your case:

add_filter( 'sftth_taxonomies', 'my_taxonomies_with_thumbnail' );

function my_taxonomies_with_thumbnail( $taxonomies ) {
    return array( 'my_custom_tax' => 'my_custom_tax', );
}

After 5 months, I guess I can mark this topic as resolved.

I have the same issue and your answer works fine for me.

This topic is resolved.
Thanks!