wpml_post_edit_meta_box_context
This filter defines where to place the WPML post edit meta box.

WPML Version: 4.2.8

This filter defines where to place the WPML post edit meta box.

side

This will display the WPML language box in the sidebar.

normal

This will display the WPML language box beneath the main editor.

advanced

The same as “normal” but with lower priority. So, if you have two meta boxes, one with context set to normal and the other set to advanced, the box with the normal context will be displayed first/before.

add_filter('wpml_post_edit_meta_box_context', function (){
    return 'normal';
});