Add this code to the Custom CSS field on the Appearance tab of your YouTube Gallery widget’s settings:
.global-styles,
.yottie-widget-video,
.yottie {
margin: 0 auto !important;
}
.yottie-widget-video,
.yottie-widget-video iframe,
.yottie-widget-video-preview-thumbnail img,
.yottie-widget-video-preview-thumbnail {
max-width: 342px !important;
height: 350px !important;
}
.yottie-widget-video-preview-thumbnail img {
object-fit: cover;
}
.yottie-widget-feed-section-slide {
display: flex;
}