WordPress at a glance
action is not described

post_submitbox_start action-hook . WP 2.7.0

Fires at the beginning of the publishing actions section of the Publish meta box.

Usage

add_action( 'post_submitbox_start', 'action_function_name_3224' );
function action_function_name_3224( $post ){
	// action...
}
$post(WP_Post/null)
WP_Post object for the current post on Edit Post screen, null on Edit Link screen.

Changelog

Since 2.7.0 Introduced.
Since 4.9.0 Added the $post parameter.

Where the hook is called

post_submit_meta_box()
post_submitbox_start
link_submit_meta_box()
post_submitbox_start
wp-admin/includes/meta-boxes.php 329
do_action( 'post_submitbox_start', $post );
wp-admin/includes/meta-boxes.php 1069
do_action( 'post_submitbox_start', null );

Where in WP core the hook is used WordPress

Usage not found.