Is there a way to show if an object or document is pinned in a view? either with an icon, or a column with a property definition?

I don't think this is currently possible unfortunately. As far as I understand the "pinned state" is not a property of the object itself like the checked out state but kept in a separate user-specific list.

Users can see if a certain object is pinned by selecting it in the view and checking the pin icon on the metadata card:

Is this something that could be requested as a feature? ideally built in PD that could be used as a column for the user but alternatively a method of some sort to lookup if the value has been pinned and by whom (kind of like "checked out by" though I understand it adds the complication of multiple people pinning it.