#1. All Gallery Grid
Use this code to Custom CSS box
div.gallery-grid.gallery-grid--layout-grid {
padding-left: 8vw !important;
padding-right: 8vw !important;
}

#2. Gallery Grid on Desktop Only
Use this CSS code
@media screen and (min-width:768px) {
div.gallery-grid.gallery-grid--layout-grid {
padding-left: 8vw !important;
padding-right: 8vw !important;
}
}

#3. Gallery Grid on Mobile only
Use this CSS code
@media screen and (max-width:767px) {
div.gallery-grid.gallery-grid--layout-grid {
padding-left: 8vw !important;
padding-right: 8vw !important;
}
}

#4. Gallery Grid on One Page
First, you need to find the Page ID. Follow this.
In my example, we will have:
- #collection-66067426a799765085da1057

Next, use this CSS code
#collection-66067426a799765085da1057 div.gallery-grid.gallery-grid--layout-grid {
padding-left: 8vw !important;
padding-right: 8vw !important;
}
#5. Specific Gallery Grid
First, you need to find Gallery Grid Section ID. Follow #4 tool.
In my example, we have:
section[data-section-id="660fb69c5ad8264c5dbae2e7"]

Next, use this CSS code
section[data-section-id="660fb69c5ad8264c5dbae2e7"] div.gallery-grid.gallery-grid--layout-grid {
padding-left: 8vw !important;
padding-right: 8vw !important;
}