Taxonomies

You need to navigate to your theme config in themename/app/config.php and find $taxonomies variable. That is a simple array. To insert a taxonomy just add a new value like:

'gallery-category' => array(
	'for'		=> array( 'gallery' ),
	'config'  	=> array(
		'sort' 			=> true,
		'args' 			=> array( 'orderby' => 'term_order' ),
		'hierarchical' 	=> true,
	),
	'singular'	=> 'Category',
	'multiple'	=> 'Categories',
),

The structure is the same as for register_taxonomy function, described in https://codex.wordpress.org/Taxonomies with one exception that we have added Singular and Multiple keys to generate all required labels automatically.