I’m wondering if I can request a feature to be rendered. I know this is possible, but it may be that the feature is too niche.
We have waterway=weir represented as a dotted grey line across the water. See here.
Almost always, a weir also has a sluice gate, but if you map this, it doesn’t appear on the map - the physical barrier across the river appears to have a break in it. I think it would be good if it rendered like the weir, or perhaps very slightly different.
Taken together, as far as I can see there are ~500 instances of
waterway=flow_control + flow_control=sluice_gate.