Possible to setup trial individual Passkey account, then add to existing Family plan?

Thanks Dave,
For now it would appear to be a non-starter unless I wanted to spin-up a test account at cost.
I don't suppose there is a way to see my items with Passkeys associated with them already?
I already have quite a few accounts with Passkeys turned on, but would like greater visibility to see beyond just what accounts DON'T have Passkeys turned on. Especially as it's clearly still early days, or inaccurate to say that some of these accounts even support Passkeys properly.
Tracking items with Passkeys associated to them, ratios against the rest of the vault, would be helpful for broader Watchtower metrics.