Meta Box

Is there a possibility to see or extract the code?

Maybe just use var_dump or print_r?

If you don't mind, please give me the post to register meta boxes. I can check that for you.

I guess you probably add filter too soon, when the get_the_terms function doesn't exists. You might want to change your code to something like:

add_action( 'after_setup_theme', function() {
    add_filter( 'rwmb_meta_boxes', 'prefix_register_meta_boxes' );
} );

This way, your function runs at after_setup_theme where all WP functions are available.

The group field doesn't auto turn the oembed URL into the video. To do that, you need to use a helper code, like this:

$url = $group['paragraph_movie'];
echo RWMB_OEmbed_Field::get_embed( $url );

That's correct! I forgot that you're using the Builder extension 🙂

I'm not sure I get what you want! I think using WPML for translation always put something in the DB.

Maybe you should localize your theme/plugin using .po file. Then use poEdit to make translation. That way there's nothing stored in the DB (and you also don't use WPML).

Did you try this docs? https://wpml.org/documentation/getting-started-guide/string-translation/

I see!

Does your code above work? Because if you set your custom column sortable that way, WordPress simply sets orderby=navn and you have to hook to pre_get_posts to filter by that.

By the way, to add sortable columns, you don't need to add a new filter to the extension. WordPress has that filter already (that the extension uses). You can refer to this article for more info:

https://code.tutsplus.com/articles/quick-tip-make-your-custom-column-sortable--wp-25095