I wouldn’t know how to implement it properly, but would love to see someone pick it up For reference I had posted a feature request here as well: Add a data-tag-group attribute for tags
As mentioned there I believe the technical implementation would be more aligned with Discourse defaults if it wouldn’t be assigned a class but a data attribute as classes are usually applied for common styles, not for unique identifiers. Also, tags already have the data-tag-name attribute, so a data-tag-group attribute seems to fit right in.
For styling in CSS, there’s no advantage to have a class. It’s just as straightforward to declare styles based on the attribute ([data-tag-group: "group-name"]).
Also, don’t want to hijack your marketplace topic @jrgong, so please flag or move to my feature request if you think it is!
But I’d still believe if this is also to be generally adopted, it would be both more descriptive and aligned with common attribute naming to use the actual name. So on the tag element it would look like: