Hi Long,
I already tried with the solution you prospect, but the results is similar to set display: none in CSS and this solution doesn't impact on load time.
What I expect to find, is a solution that consent me to completely prevent loading the custom fields until user explicitly make a request for clicking the button (then I retrive the code by an Ajax call).
My only problem whit this solution are the remove buttons, because even if the callable function for the filter rwmb_{field_id}_html return null value, the remove buttons are still on page.
So, how can I prevent the load of the return buttons if the callable function return null?
