Harvest understands CM metdata and can post metrics for any CM counter type including 2D and 3D arrays. So the CIFS histogram one you mentioned should work fine. If you add them to a custom template that is already using a plugin to do some summarization you do need to verify that post logic is compatible with your newly added counters. For cdot-cifs it seems the plugin only replaces slashes needed for a counter named Open/Close so no issue there, but for others like volume if you want a roll-up vol_summary metrics created you might have to adjust.
So for 8.3 you could update to add the one in red:
Great job to extend Harvest for your needs, this is exactly what I hoped people would do!
Indeed, I didn't understand your label mapping table but now I get it that you added that snippet to the overrides table and not the main poller hash. Maybe I should edit Harvest to detect labels that include <>= and replace them with gt, lt, and eq. Thoughts? Because Graphite allowed them (I think = as well but not positive) it hasn't come up before. But if Grafana has trouble them maybe it is something to modify across the board.