#1. First, install Squarespace ID finder and find the ID of 2 Gallery Slideshows
In my example, we will have:
section[data-section-id="6655814af27321176a65fb4e"]
and
section[data-section-id="6655814af27321176a65fb50"]
and page ID:
#collection-6655814af27321176a65fb4d

#2. Use this code to Custom CSS box
/* Side by side Slideshow */
body#collection-6655814af27321176a65fb4d:not(.sqs-edit-mode-active) {
& {
overflow: hidden;
}
@media screen and (min-width:768px) {
section[data-section-id="6655814af27321176a65fb4e"], section[data-section-id="6655814af27321176a65fb50"] {
width: 50% !important;
float: left !important;
padding: 0px !important;
height: 100vh !important;
}
}
@media screen and (max-width:767px) {
.gallery-fullscreen-slideshow {
height: 50vh !important;
}
}
.gallery-fullscreen-slideshow {
margin-bottom: 0px !important;
}
}

#3. Result

#4. Note:

#5. Explain code
