Notice: This is an unsupported customization . If you break something you’re on your own Shopify support will not help you and will have to pay someone to fix it.
Editing robots.txt feature is rolling out, should have generally availability by monday, so far for all plans.
Bigger thread https://community.shopify.com/c/Shopify-Discussion/How-can-I-edit-robots-txt/m-p/1212458/highlight/true#M245647
https://help.shopify.com/en/manual/online-store/themes/theme-support#shopify-design-policy
Be careful while you can make it so more tags are crawl tags can be applied in any order risking duplicate content SEO penalties.