When working in views, there's a lot of help to get the syntax for custom fields (button Insert Field). But there's nothing for custom taxonomies attached to posts, is that right? I'm supposed to use WordPress functions like mb.wp_get_post_terms, check with mb.count if it returned terms, etc?
Just wanting to make sure I am not missing an easier way to deal with this.
Yes, the fields in the Insert Field tab are some basic and registered custom fields for objects (post, term, user) and the settings page. If you want to work with PHP and WordPress functions for some advanced cases, you also need to have basic knowledge about Twig code.
Perhaps for a feature version of Views it would be a good idea to also add some help for working with taxonomies that are related to the post. That's pretty common. Almost all my custom post types have custom fields as well as custom taxonomies.