To change Summary Block (Carousel) arrows to custom icon, you can use this code to Custom CSS box. Replace example icon url with your icon url.
div.summary-v2-block .sqs-gallery-controls .next, div.summary-v2-block .sqs-gallery-controls .previous {
background-image: url(https://content.invisioncic.com/p289038/monthly_2023_04/heart-arrow-left.png.dc3b32b710c169a07350cba2c41abf04.png);
background-size: contain;
background-repeat: no-repeat;
background-position: center;
background-color: transparent !important;
}
div.summary-v2-block .sqs-gallery-controls .previous {
background-image: url(https://content.invisioncic.com/p289038/monthly_2023_04/heart-icon-right.png.b1403153d4b4a22c29b1cc99f821210a.png) !important;
}
div.summary-v2-block .sqs-gallery-controls .next:before, div.summary-v2-block .sqs-gallery-controls .previous:before {
visibility: hidden;
}
result
