[Tagging] tributary role in waterway relations: widespread?

[David Marchal]

Hello, there.

I wondered: I saw the' tributary' role on some waterway relations; while I understand its usage — to represent the fact that a waterway flows into another —, I would like to know if it is widespread or even widely accepted, if not voted on wiki, as JOSM complains about not knowing it every time I use it.

Awaiting your answers,

Regards.