Is commit groups a feature or a wish list? I hadn't heard of it before but a Duck Duck Go search only throws up a blog post discussing the desirability for such a feature in git.
You can get something somewhat similar with "always create merge commit" workflows (no fast forward) and changing your tooling to look at the first-parent-history by default. This view will have one commit per merge, but you can choose to follow the second+ parent history for a given commit to see what went into it.
Or just include a group name in the commit message. No need for empty merge requests in your history. Since most people use issue tracking systems, just prepend the issue number to each commit message in the group.