Using MetaBox.io to create subsgroups.

gistfile1.txt

<?php
$groups = rwmb_meta( 'ie-slider-sliders' );
foreach ( $groups as $group ) {
	
	// Field slider:
	$subgroups = $group[ 'slider' ] ?? '';
	foreach ( $subgroups as $subgroup ) {
		
		// Field title:
		echo $subgroup[ 'title' ] ?? '';
		
		// Field image:
		$image_ids = $subgroup[ 'image' ] ?? [];
		?>
		<h3>Uploaded images</h3>
		<ul>
			<?php foreach ( $image_ids as $image_id ) : ?>
				<?php $image = RWMB_Image_Field::file_info( $image_id, [ 'size' => 'thumbnail' ); ?>
				<li><img src="<?php echo $image['url']; ?>"></li>
			<?php endforeach ?>
		</ul>
		<?php
		
		// Field caption:
		echo $subgroup[ 'caption' ] ?? '';
		
		// Field description:
		$values = $subgroup[ 'description' ] ?? '';
		foreach ( $values as $value ) :
			echo do_shortcode( wpautop( $value ) );
		endforeach;	
	}

}
?>