There are various format options available for slideshows, including a vertical display ideal for mobile devices.
If you would like to display a particular slideshow for mobile or desktop display only, first begin in the project’s Photos tab, click on the three dots in the top right corner of your slideshow, and select the Hide Slideshow option.
Click on the dropdown to select the slideshow visibility. You can choose to hide or make the slideshow visible in general, show in gallery on mobile only, or show in gallery on desktop only. Then click Apply.
