Panel hanging hardware
I'm afraid I'm not sure what that plastic harness might be. Would it be at all possible to see a photo of the part in question clearly and without obstruction?
The part fell to the grass and dirt outside. Unable to retrieve it.
It is a plastic part that has groove on the side to ease sliding when the vertical link goes up and down when the crank operates.
It also has a metal cover to ensure the jalhousie panel hanger eye goes over.
The metal cover is probably added for durability.
These parts are where the rivet goes through.
I am sorry I Don't have a picture of it
I'm afraid I don't know what it might be. A verbal description is not enough at this stage. This is a fairly old fashioned window and repair parts aren't commonly being made. The only way we can check to see if we have something is if we can see the part in question.
I'm sorry for the inconvenience.