How do I add image slides in Gutenberg?
[nivo] shortcode, while editing content using the Gutenberg editor you can use the Image or Gallery block and then simply delete the block. Alternatively you can use Set Featured Image and upload multiple images that way.
How to control the sequence of slides in nivo
If you have a set of images that you want to display in a nivo slider and control the sequence in which they are displayed then you can use the
id=parameter to list the post IDs in the required order.