Hi Long,
Thank you for your reply, I am not very familiar with php yet, I think I might need the page or post URL stored into a variable, that I can grab with the dynamic Slider plugin. For now, if I type manually or copy paste the URL into the URL custom field, it works. But I wonder if it is possible to select the page like on the post field, and obtain its URL, while still staying in the WordPress admin backend, because then I need to grab the URL variable from the Smart Slider dynamic slide.