I’m not sure that that worked, unfortunately. I don’t see a way to add multiple photos in that option. Let me ask in a different way: is there a way to have, for example on the Slider image, multiple images that slide left/right within the same frame?
If you want to add slider images then you will need to follow the steps below
Go to dashboard > slider > add new > add title/description > add featured image > click on publish/update
repeat the step to add another image for the slider to slide.
You can not add multiple image at once for slider.
I’ve tried the steps you mentioned — but when I add new sliders, with new images, I cannot see them on my actual page in the appearance editor. I’m sorry I’m not getting it — do you have another way of explaining this?