Importing PRODUCT / MODEL files

If you're trying to import a file that has this sort of structure:

You're going to run into a few issues:

1. Variations do not have title/content data.
2. Variations do not have prices or images.
3. Parent products have stock listed but it'd be better to manage stock on a variation level.

To import these products properly you should use the {product_id[1]} element along with the "All variations for a particular product have the same title as the parent product" option from WP All Import's official documentation (see documentation) while making these changes:

Title

In the title section, add some elements so that the variations will have titles:

Stock

You should use the {model_quantity[1]} element for the stock since we're going to manage it on the variation level:

Prices in Custom Fields

In the Custom Fields section import the prices into fields named "_custom_regular_price" and "_custom_sale_price":

Code in the Function Editor

Next, we need to save the following code inside the Fucntion Editor:

function wpai_wp_all_import_variable_product_imported( $post_parent ) {
    global $wpdb;
    if ( $results = $wpdb->get_results( 'SELECT `ID` FROM `' . $wpdb->prefix . 'posts` WHERE `post_parent` = "' . $post_parent . '" AND `post_type` = "product_variation"' ) ) {
        $parent_product = wc_get_product( $post_parent );
        $regular_price = $parent_product->get_meta( '_custom_regular_price', true );
        $sale_price = $parent_product->get_meta( '_custom_sale_price', true );
        $price = ( ! empty( $sale_price ) && $sale_price < $regular_price ) ? $sale_price : $regular_price; 
        $main_image = $parent_product->get_image_id();
        $parent_product->set_manage_stock( 'no' );
        $parent_product->delete_meta_data( '_custom_regular_price' );
        $parent_product->delete_meta_data( '_custom_sale_price' );

        foreach ( $results as $variation ) {
            $var_product = wc_get_product( $variation->ID );
            $var_product->set_regular_price( $regular_price );
            $var_product->set_sale_price( $sale_price );
            $var_product->set_price( $price );
            $var_product->set_image_id( $main_image );
            $var_product->save();
        }

        $parent_product->set_regular_price( null );
        $parent_product->set_sale_price( null );	
        $parent_product->save();

        update_post_meta( $parent_product->get_id(), '_price', $price );
    }
}

add_action( 'wp_all_import_variable_product_imported', 'wpai_wp_all_import_variable_product_imported', 10, 1 );

This will turn off stock management for the parent product, then copy the prices and images from the parent to all of its variations.