Sorry for the trouble!
We're working to bring the slideshow button back.
For now, you can insert a slideshow with the [slideshow] shortcode, provided that the images have already been uploaded through the post or page.
1. Open the post or page for editing.
- 1b. Upload images via the post or page if they have not been uploaded yet.
2. Place the cursor where the slideshow will be.
3. Type [slideshow]
4. Click Update to publish the changes.