I have a technical SEO question for collection pages. How do I go about adding the ListItem schema for each product on a collection page?
See image below as an example.
Any help would be really appreciated 
So this is kinda interesting. As far as I can tell there’s not really a Google recommended way to handle collection aka category aka PLPs in terms of structured data. There’s the featured Carousel search result type, which I’m assuming thats what the ItemList > ListItem schema is trying to do? To me this doesn’t quite fit the intention of a Shopify collection PLP though. The two most common considerations regarding structured data are to trigger rich results, and also to improve how Google “understands” your content. I haven’t seen or done any robust testing as to which schema setup on PLPs is preferable in ecom, so interested to find out more here if you know!
But overlooking the reasons why you want to do it, how to implement it’s either: use an app that does it for you, or custom code it. There are ways to loop through product items per page of a Shopify category, so as long as you know the exact schema pattern to output, should be straightforward for a dev to code it up.
Some SEO apps on Shopify eg SmartSEO implement this exact setup (is that where you got the screenshot?) others like the app “JSON-LD for SEO” don’t even bother with any list type of PLP structured data.