Assigning user with custom role as author to posts in WordPress
For now, there’s a workaround: add level_1 capability to your custom role.
add_role('custom_role', 'Custom Role', array( 'level_1' => true ... ) );
$role = get_role('custom_role'); $role->add_cap('level_1');
Notice: if you already had users in your Wordpres, to take effect you need to temporary change user’s role to another role, save and then back to your custom role.