Star Rating System

1. You would remove that snippet.
And use this instead:

function make_star_bar() {
    $rating = get_post_meta( get_the_ID(), 'rating', true );
	if ( $rating ) {
        $color = '#f00';
        $prefix = 'star-bar-';
        $uniqueClass = uniqid($prefix);
        $percentage = 100 * $rating / 5;
        $html = '<span class="'.$uniqueClass.'">★★★★★</span>
        <style>
        .'.$uniqueClass.' {
            background: linear-gradient(90deg, '. $color  . ' ' . $percentage .'%, rgba(0,0,0,0) '. $percentage.'%);
            color: rgba(0,0,0,.2);
            background-clip: text;
            -webkit-background-clip: text;
            color: rgba(0,0,0,.2);
        }
        </style>
        <script type="application/ld+json">
        {
            "@context": "https://schema.org",
            "@type": "Rating",
            "ratingValue": "' . $rating . '",
            "bestRating": "5",
            "worstRating": "1"
        }
        </script>
        ';
        return $html;
	}
}
add_shortcode('star_bar', 'make_star_bar');

2. Then create a Block Element Hook in Appearance -> Elements:

https://docs.generatepress.com/article/block-element-hook/

2.1 Add your Content and the [star_bar] shortcode to the element.
2.2 Set the Hook to after_entry_title
2.3 Set the Display Rule Location to where its required eg. Post > All Posts

3. Publish that Element.

4. Now you need to create a Custom Field on your post called: rating - which is where you will add the rating value for each post.

Unfortunately, it not working despite completing all 4 steps... Only showing [star_bar]. I also noticed the star rating appears if I add the shortcode [star_bar stars="2.6"] directly to the post, although it takes the value from the custom field now ( I add the shortcode [star_bar stars="2.6"], but it shows 4 stars entered in custom field).

Did you remove that other function ? And clear any caches ?

Yes, here are the screenshots:

https://ibb.co/Gc9m5Q7
https://ibb.co/ZVLYVt7
https://ibb.co/y0WQpJN
https://ibb.co/QJLjtmz
https://ibb.co/Nrn6wXc

What i mean is, do you still have the other snippets saved anywhere ?

nope, just tried to test if the new snippet works with the old shortcode [star_bar stars=”2.6″] and it did. Anyway it's not working with Custom Field: rating

I tested the steps i added here:

https://generatepress.com/forums/topic/star-rating-system/page/3/#post-2548930

And this my ACF Field:

https://www.screencast.com/t/kS9Z4DwuodN

And that works as intended using the [star_bar] shortcode.

So i am not sure why it won't work for you.

Still not working;/// Where do you put the actual rating value, and in what format? E.g I'm trying to add 4.0 or 4 in the custom field but it doesn't change anything...

My ACF Field Group has is set to Display on ALL posts:

https://www.screencast.com/t/XSExDdEd

then in the single Post editor, i added the value in the ACF field.

My settings are the same, although I also tried to test for 1 post only. And nothing has changed, I have the same issue, the [star_bar] appears instead of the visual star rating...

If you want to raise a new topic, and use the Private Information field to provide me an admin login i can take a closer look.

Hey David, are you still available for help?

If you can raise a new topic, where you can share a link to the site then i can take a look.
I cannot say i can make it work, as it iss custom development. But i am happy to look.

The new topic with private info created.