invoice pdf does not show custom fields

Ok @wienermischung

This problem can be resolved by adding two filters to functions.php file.

The first filter will allow data to be passed between the Flexible Checkout Fields plugin and the invoice generation plugin used in the shop.

function add_custom_field_to_address_formats( $formats ) {
    foreach ( $formats as $country_code => $format ) {
        // Add the custom field placeholder to the end of each format
        $formats[ $country_code ] = $format . "\n{custom_field}";
    }
    
    return $formats;
}
add_filter( 'woocommerce_localisation_address_formats', 'add_custom_field_to_address_formats', 10, 1 );

You have to add a placeholder from the Flexible Checkout Fields plugin for each or selected country… the placeholder will be the meta name without the “_billing”, i.e., from the image it will simply be “{test}”.

And the second one, resolving formatting issues. To resolve the formatting issue, you need to define this precisely by editing the string e.g. “{company}\n{name}\n{address_1}\n{address_2}\n{postcode} {city}\n{country}” and adding the appropriate placeholders and newline characters there “\n”

// this is just to show what placeholders are available, and is not needed when second filter will be used
add_filter( 'woocommerce_formatted_address_replacements', function( $placeholders, $args ) {
    print '<pre>';
    print_r( $placeholders );
    print '</pre>';
    return $placeholders;
}, 10, 2 );

// this is the only filter needed - but needs to be adjusted
add_filter( 'woocommerce_localisation_address_formats', function( $formats ) {
    foreach ( $formats as $country_code => $format ) {
        // here we add custom field at the end of each format
        // $formats[ $country_code ] = $format . "\n{custom_field}";
        // but (alternatively) we can define full format for each country - see available placeholder by running the code above
        $formats[ $country_code ] = "{name}\n{company}\n{address_1}\n{address_2}\n{city}\n{state}\n{postcode}\n{country}\n{custom_field}";
    }
    
    return $formats;
}, 10, 1 );