Move caption over Gallery Reel Image

#2. Use this code to Custom CSS box to move caption over images

figcaption.gallery-caption.gallery-caption-reel {
    opacity: 1 !important;
    visibility: visible !important;
    position:absolute;
    top: 50%;
    left:50%;
    transform: translate(-50%,-50%);
    margin: 0 !important;
    height: auto !important;
}

Result

#3. If you want to apply it for specific gallery reel, you can find Reel ID.
Then use CSS code like this

section[data-section-id="66d41e080d7e43167a4dadad"] figcaption.gallery-caption.gallery-caption-reel {
    opacity: 1 !important;
    visibility: visible !important;
    position:absolute;
    top: 50%;
    left:50%;
    transform: translate(-50%,-50%);
    margin: 0 !important;
    height: auto !important;
}