I added a Image Select Field with a couple options like so:
value:https://the-million-posts--site.tukutoi.com/wp-content/uploads/2020/12/a5d8ffad-19df-3aa9-9e06-870146871026.jpg
value: https://the-million-posts--site.tukutoi.com/wp-content/uploads/2020/12/a79b4e0b-a842-300a-a503-8288e4e8603c.jpg
I use AIO, and this is the code it generates:
add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );
function your_prefix_register_meta_boxes( $meta_boxes ) {
$prefix = '';
<pre><code>$meta_boxes[] = [
'title' => esc_html__( 'Usdfagdhntitled Field Group', 'text-domain' ),
'id' => 'usdfagdhntitled-field-group',
'post_types' => ['post'],
'context' => 'normal',
'priority' => 'high',
'fields' => [
[
'id' => $prefix . 'image_select_8n1slce1j5p',
'type' => 'image_select',
'name' => esc_html__( 'Image Select', 'text-domain' ),
'options' => [
'value' => esc_html__( 'https://the-million-posts--site.tukutoi.com/wp-content/uploads/2020/12/a79b4e0b-a842-300a-a503-8288e4e8603c.jpg', 'text-domain' ),
],
],
],
];
return $meta_boxes;
}
We can see it adds only one option, and that is also what I see in the Post Edit Screen: just one option.
I tried to store the code in the functionsphp and add the other options manually like so
'options' => [
'value' => esc_html__( 'https://the-million-posts--site.tukutoi.com/wp-content/uploads/2020/12/a79b4e0b-a842-300a-a503-8288e4e8603c.jpg', 'text-domain' ),
'value' => esc_html__( 'https://the-million-posts--site.tukutoi.com/wp-content/uploads/2020/12/537f927b-2c14-3162-8a44-c0ac6c39fc8f.jpg', 'text-domain' ),
],
But it still offers only one image.
I have tested this with Theme 2021 and no other plugins...