[David Birdwell]

From the standpoint of a viewer and occasionally as a player from afar, it can be difficult to tell if a call was made by the offense or by the defense. An optional signal that demonstrates if the call was made by the offense or the defense would be useful.

[amaury]

This already exists, see hand signals https://rules.wfdf.sport/wp-content/uploads/2022/01/WFDF-Rules-of-Ultimate-2021-2024-Hand-Signals.pdf number 23:

23. Who made the call
Called by Offence / Defence
Pointing with two arms straight out, towards the end zone being defended by the team