I don’t think you can combine [details] with the slideshow.
You can remove the details and add a table of contents to your OP How to Add a Table of Contents (TOC) to Your Posts if you want to use the slideshow. Or you can link to each individual update post like I did in mine PFM's Collection Thread
or if you really want to use the details collapse you can switch your gallery over to [grid] [/grid] to squish the images down and allowing a fullscreen slideshow on click like below:
Original Post
Hello E4! I’m new here, wanted to share my eevee collection. My goal is a complete set of graded artwork - that is, one of each Eevee artwork but not necessarily print duplicates (such as Radiant collection vs sylveon trainer kit, battle decks, etc. Wish me luck!
what it looks like:
[details="Original Post"]
Hello E4! I'm new here, wanted to share my eevee collection. My goal is a complete set of graded artwork - that is, one of each Eevee artwork but not necessarily print duplicates (such as Radiant collection vs sylveon trainer kit, battle decks, etc. Wish me luck!
[grid]
[/grid]
[/details]