I tried to set up a this field using the cmb2 widget snippet without luck to get it working
The field definition is:
array(
'name' => 'Test',
'type' => 'select',
'multiple' => true,
'options' => array(
'1' => __( 'Option 1' ),
'2' => __( 'Option 2' ),
'3' => __( 'Option 3' )
),
I always got the default value :/