Worryingly some of the most basic of microdata is missing.

Although some of this can be done by workarounds outside of the cart software this would be really missing the point big time. It will likely be missed by most installations, despite this being extremely important information to be picked up by search engines, so that your website ranks properly and shows up in the best way possible when people search for your business or products. The Main Settings admin page should really be the place where much of this is included and then published in the correct way throughout the website pages which is absolutely crucial for people with little experience to no experience.

Here are just a few:

Breadcrumbs
https://developers.google.com/search/docs/data-types/breadcrumb

Sitelinks Search
https://developers.google.com/search/docs/data-types/sitelinks-searchbox

Contact Information
https://developers.google.com/search/docs/data-types/corporate-contact

Social Profile
https://developers.google.com/search/docs/data-types/social-profile

Listings Markup
https://developers.google.com/search/docs/guides/mark-up-listings

Business Information
https://developers.google.com/search/docs/data-types/local-business

Business Reviews (not product reviews)
https://developers.google.com/search/docs/data-types/review

A complete list of microdata is here: https://developers.google.com/search/docs/guides/search-gallery

John