Create a shortcode in a plugin showing the content - wordpress

Question

I want to create a shortcode in an existing Wordpress/Woocommerce plugin. Where do I put the code to create the shortcode?
The plugin displays a table with all the available variations on any given variable product on the product page.
The table reacts to what the customer selects on the attributes form.
I want to make a shortcode so that I can show this in a tab on the product page instead of before the add to cart button as is now. Where should I put the code for the shortcode?
<?php
/*
Plugin Name: Variations On Product Page
Description: Display all the available variations on the product page
Version: 1.2
*/
define( 'VARIATIONS_ON_PRODUCT_VER', '1.2' );
define( 'VARIATIONS_ON_PRODUCT_PATH', plugin_dir_path( __FILE__ ) );
define( 'VARIATIONS_ON_PRODUCT_URL', plugin_dir_url( __FILE__ ) );
require_once 'settings.php';
if ( ! isset( Variations_Product_Settings::getSettings()['enabled'] ) ) {
return;
}
add_action( 'wp_enqueue_scripts', function () {
wp_enqueue_script( 'variations-on-product', VARIATIONS_ON_PRODUCT_URL . 'assets/variations-on-product.js', [ 'jquery' ], VARIATIONS_ON_PRODUCT_VER );
wp_localize_script( 'variations-on-product', 'variations_on_product_settings', apply_filters( 'variations_on_product_js_settings', [
'options' => Variations_Product_Settings::getSettings(),
] ) );
wp_enqueue_style( 'variations-on-product', VARIATIONS_ON_PRODUCT_URL . 'assets/variations-on-product.css', [], VARIATIONS_ON_PRODUCT_VER );
} );
add_action( 'woocommerce_before_add_to_cart_button', function () {
global $product;
/* #var WC_Product $product */
if( !$product->is_type('variable') ) return;
?>
<style>
#product-variations .attachment-woocommerce_thumbnail {
max-width: 100px;
}
table#product-variations .custom_form .quantity {
float: none !important;
width: 100% !important;
margin-right: 0 !important;
}
table#product-variations .custom_form .input-text.qty {
width: 100% !important;
box-sizing: border-box;
}
table#product-variations .custom_form button.button.alt {
width: 100%;
}
table#product-variations .custom_form p.stock {
margin-bottom: 3px !important;
text-align: center;
font-size: 14px
}
</style>
<table id="product-variations">
<thead>
<tr>
<?php if( !Variations_Product_Settings::getSettings()['hide_thumbnail'] ): ?>
<td>Image</td>
<?php endif; ?>
<td>Title</td>
<td>Price</td>
<td>*</td>
</tr>
</thead>
<tbody></tbody>
</table>
<?=Variations_Product_Settings::getSettings()['load_more_text'] ?: 'Load more'?>
<?php
} );
add_filter( 'woocommerce_available_variation', function ( $default, $product, $variation ) {
/* #var WC_Product_Variation $variation */
ob_start();
?>
<tr>
<?php if( !Variations_Product_Settings::getSettings()['hide_thumbnail'] ): ?>
<td>
<?= $variation->get_image() ?>
</td>
<?php endif; ?>
<td>
<?= $variation->get_name() ?>
<p>
<small><?= $variation->get_sku() ?></small>
</p>
</td>
<td>
<?= $variation->get_price_html() ?>
</td>
<td>
<?php if ( $variation->is_in_stock() ) : ?>
<form class="custom_form" action="<?php echo esc_url( get_permalink() ); ?>" method="post" enctype='multipart/form-data'>
<?php
if( !Variations_Product_Settings::getSettings()['hide_stock_status'] ) {
if ( $variation->managing_stock() ) {
echo wc_get_stock_html( $variation );
}
}
?>
<?php
if( !Variations_Product_Settings::getSettings()['hide_qty'] ) {
woocommerce_quantity_input( [
'min_value' => apply_filters( 'woocommerce_quantity_input_min', $variation->get_min_purchase_quantity(), $variation ),
'max_value' => apply_filters( 'woocommerce_quantity_input_max', $variation->get_max_purchase_quantity(), $variation ),
'input_value' => isset( $_POST['quantity'] ) ? wc_stock_amount( $_POST['quantity'] ) : $variation->get_min_purchase_quantity(),
] );
}
?>
<button type="submit" name="add-to-cart" value="<?php echo esc_attr( $variation->get_id() ); ?>" class=" button alt"><?php echo esc_html( $variation->single_add_to_cart_text() ); ?></button>
</form>
<?php endif; ?>
</td>
</tr>
<?php
$default['c_template'] = apply_filters('vop_variation_template', ob_get_clean(), $variation);
return $default;
}, 10, 3 );
// Hide add to cart on product
if ( isset( Variations_Product_Settings::getSettings()['hide_product_addtocart'] ) ) {
add_action( 'woocommerce_before_add_to_cart_button', function () {
?>
<style>
.single_variation_wrap {
display: none !important;
}
</style>
<?php
} );
}
I tried to add the following code but did not work.
<?php
/*
Plugin Name: Variations On Product Page
Description: Display all the available variations on the product page
Version: 1.2
*/
add_shortcode( 'minkod', 'mitt_lilla_shortcode_handler' );
define( 'VARIATIONS_ON_PRODUCT_VER', '1.2' );
define( 'VARIATIONS_ON_PRODUCT_PATH', plugin_dir_path( __FILE__ ) );
define( 'VARIATIONS_ON_PRODUCT_URL', plugin_dir_url( __FILE__ ) );
I added the function:
function mitt_lilla_shortcode_handler () {
$myshortcode ='
add_action( 'woocommerce_before_add_to_cart_button', function () {
global $product;
/* #var WC_Product $product */
if( !$product->is_type('variable') ) return;
?>
And in the end:
> <style>
> .single_variation_wrap {
> display: none !important;
> } </style> <?php } ); ';} return $myshortcode; }