Do not see any reason not to copy over the flag of the old, existing IDProp to the new one when assigning (e.g. `C.object['prop'] = 0.5` would nuke that IDProp flag).
Do not see any reason not to copy over the flag of the old, existing IDProp to the new one when assigning (e.g. `C.object['prop'] = 0.5` would nuke that IDProp flag).