No problem.

The only custom filter which is currently included to URE’s code related to the edit restrictions items at user level is ‘ure_post_edit_access_authors_list’.

$value = apply_filters('ure_post_edit_access_authors_list', $value);

I will add more custom filters with a next version possibly.

You may use a general WordPress ‘get_user_metadata’ filter from get_meta_data() function:

$check = apply_filters( "get_{$meta_type}_metadata", null, $object_id, $meta_key, $single );

$object_id : $current_user->ID,
$meta_key : $wpdb->prefix .’ure_categories_list’

In both cases you should check if you set the category for this user or not yourself inside those filters.