Hello Jonathan,
What you have in mind may require custom coding. You will need to query the database extracting the number of sliders, it’s name and shortcode before it can be loaded into a dropdown selector as one of the custom fields. Regretfully, this particular customization request is outside the scope of our support as this is not related to an issue with the theme and instead has to do with your customization of it. As such, you will need to investigate this particular request on your own or seek help from a developer should you not feel comfortable making these changes yourself. If you have any further questions about the theme, we are more than happy to provide you with assistance on these inquiries.
Thank you for your understanding.