These steps will help you create a “show more reviews” button in Product Detail Page, like this.

when clicking on button >> show more reviews

#1. First, you use this code to Custom CSS box.
div.btn {
cursor: pointer;
}
div.ReviewTabsTitle ~ * {
display: none;
}
.show-hide ~ * {
display: block !important;
}

#2. Use this code to Code Injection > Footer.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
<script>
$(document).ready(function() {
setTimeout(function(){
$('<div class="btn btn--border theme-btn--primary-inverse sqs-button-element--primary">Show more reviews</div>').insertAfter('.averageStarsContainer');
$('div.btn').click(function() {
$('div.ReviewTabsTitle').toggleClass('show-hide');
});
},3000);
});
</script>

#3. Note
Button will inherit Header Button Style.