I just stumbled over the tag
highway=mini_roundabout, see OSM Wiki. As far as I can see GraphHopper doesn't use this tag so far. The tricky thing about this is that it's tagged as a node in the middle of an intersection.
Here is one example and a Overpass query.
Is there a reason why we don't use this, except for "it's complicated to implement and the gain is not that big"? I couldn't find any issues or other topics about this. I think this would improve the turn instructions, but also mini roundabouts seem to be only used in some minor back roads.
WDYT? Should we create an issue in the repo for this?