Key Value field with textarea

Hi,

Yes, it is possible. We can create a new field type, extends the class RWMB_Key_Value_Field which render the field key_value and change the default input type=text for value field to textarea.

– Create a new field type custom_key_value:

if ( class_exists( 'RWMB_Field' ) ) {
    class RWMB_Custom_Key_Value_Field extends RWMB_Key_Value_Field {
        public static function html( $meta, $field ) {
            // Key.
            $key                       = isset( $meta[0] ) ? $meta[0] : '';
            $attributes                = self::get_attributes( $field, $key );
            $attributes['placeholder'] = $field['placeholder']['key'];
            $html                      = sprintf( '<input %s>', self::render_attributes( $attributes ) );

            // Value.
            $val                       = isset( $meta[1] ) ? $meta[1] : '';
            $attributes                = self::get_attributes( $field, $val );
            $attributes['placeholder'] = $field['placeholder']['value'];
            $html                     .= sprintf( '<textarea %s>' . $attributes['value'] . '</textarea>', self::render_attributes( $attributes ) );

            return $html;
        }
    }
}

– Use the new field type:

add_filter( 'rwmb_meta_boxes', 'custom_key_value_field' );
function custom_key_value_field( $meta_boxes ){
    $meta_boxes[] = array(
        'title'      => 'Custom Key Value Meta Box',
        'post_type' => 'post',
        'id' => 'custom_key_value_meta_box',
        'fields' => array(
            array(
                'name' => 'Custom Key Value Field',
                'id'   => 'custom_key_value_field',
                'type' => 'custom_key_value',
            )
        ),
    );
    return $meta_boxes;
}

For more information, please follow the documentation:
https://docs.metabox.io/custom-field-type/
https://github.com/wpmetabox/meta-box/blob/master/inc/fields/key-value.php

Thanks! Works like a charm.