For resumable receives, the data is received into the temporary %recv filesystem. Is it possible to interrogate the size or other properties of this filesystem? It is hidden, so it is unclear what zfs commands are valid for it. Additionally, it is not described much in the OpenZFS documentation, so not very clear from that perspective (understandable since it is a relatively new feature).
Of course, it would not be meant to be used before completion of the receive, but it would be useful to list how much space it is consuming, etc.