Hi Duncan,
For plugins, here’s an article that may be helpful: https://www.wpbeginner.com/best-wordpress-slider/
In terms of custom CSS, this is what can be achieved: https://share.getcloudapp.com/E0uRJBWL
To do this, add make-scrollable to the class list of the Grid Block.
Then, add this CSS through Appearance > Customize > Additional CSS:
@media (min-width: 1025px) {
.gb-grid-wrapper.make-scrollable {
flex-wrap: nowrap;
overflow-x: scroll;
}
.gb-grid-wrapper.make-scrollable > .gb-grid-column {
width: unset !important;
}
.gb-grid-wrapper.make-scrollable > .gb-grid-column > .gb-container {
width: 400px !important;
}
}