Say for example you have per circuit power monitoring, but you also have power monitoring on some individual devices, will be part of the upstream per-circuit monitoring. This would mean some energy is counted twice, once for the entire circuit, once for the individual device.
I think it would be very useful to be able to tell home assistant a given device is downstream of another, that way in the energy dashboard you could then combine certain diagrams. This could look something like (from a UK wiring perspective) “x amount of energy was used by the sockets circuit, & Y% of this was taken up by the dishwasher etc”
While this can be done with templates and a decent amount of time, I feel like this is a simple feature that could add a lot to the energy dashboard. It could drastically improve the tracking of “unknown” energy usage.