To delete any review link URL (along with any Versions of it, and any client feedback already submitted via the link) from the Commentful Figma plugin, with the Reviews tab selected in the plugin and a Review card already open, you can click on the Trash icon button in the top right of the plugin window.

If you're sure you want to permanently delete the review link, enable the Yes, I want to delete this entire review toggle, and then you can click the Delete this Shared Review button to confirm; then this will instantly and permanently delete the review URL, along with any versions of the review link that were uploaded, and any feedback that was already submitted via the review link.