I found a way to do this, but I am not very happy with this procedure. Please add your answer if you find a better way. Average time, this can be useful.
add_action('admin_head-edit.php','addCustomImportButton');
I only need this on the edit page, so I use the admin_head-edit.php , but you can use admin_head or some other (not very specific requirements)
public function addCustomImportButton() { global $current_screen;
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