As explained here, adding custom form fields is not actively supported. Thanks for your understanding.

However, in this case I’ll give you some pointers on how to deal with multiple ratings:

/**
 * Displays custom fields in the Review's "Details" metabox
 * Paste this in your active theme's functions.php file.
 * @return array
 */
add_filter('site-reviews/metabox/details', function ($metabox, $review) {
    $ratingKeys = ['rating1', 'rating2', 'rating3']; // change these as needed
    foreach ($review->custom as $key => $value) {
        if (in_array($key, $ratingKeys) ) {
            $value = glsr_star_rating($value); // render the stars from the rating value
        }
        // ...
    }
    return $metabox;
}, 10, 2);

And:

/**
 * Renders the custom review fields
 * Paste this in your active theme's functions.php file.
 * In order to display the rendered custom fields, you will need to use a custom "review.php" template
 * as shown in the plugin FAQ ("How do I change the order of the review fields?")
 * and you will need to add your custom keys to it, for example: {{ name_of_your_custom_key }}
 * @return array
 */
add_filter('site-reviews/review/build/after', function ($renderedFields, $review) {
    $ratingKeys = ['rating1', 'rating2', 'rating3']; // change these as needed
    foreach ($review->custom as $key => $value) {
        if (in_array($key, $ratingKeys) ) {
            $value = glsr_star_rating($value); // render the stars from the rating value
        }
        // ...
    }
    return $renderedFields;
}, 10, 2);

• This reply was modified 1 year, 9 months ago by Steve Stern (sterndata).
• This reply was modified 1 year, 9 months ago by Marius L. J.. Reason: Fixed missing parenthesis on posters behalf

Ah, sorry.

This:

if (in_array($key, $ratingKeys) {

Should be this:

if (in_array($key, $ratingKeys)) {

Please see the updated link: https://pastebin.com/4fvKErcp