OK, I need to combine:
– that https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/ to get the current value of current Metabox.
– and this https://www.advancedcustomfields.com/resources/acf-fields-post_object-query/ for listing all other pages following the $args, in case there is no meta value in the current post.
Now the issue is solved.
Just not sure if there is a better way to achieve?
