If I understood it right there isn’t an easy way of discovering the group a tag belongs to within the tag renderer?
This one would be great. I was using a custom CSS approach before and ditched it for this theme component with a fallback icon for all non-set tags (at least before the support for tag groups) and this is the one thing I miss.
Considering discourse-category-icons supports this, I’m guessing the renderer that replaceCategoryLinkRenderer replaces is used by the category dropdown while the renderer replaceTagRenderer replaces is NOT used by the tag dropdown, right? So maybe this would need a core change? The tag dropdown on the composer is using the replaced renderer, with icons.