you would need to create a link that contains a password of some kind…your privacy controls would need to use the URL value which would be that password of some kind to register that the link is allowed to change the data.
Probably not very secure, but doesn’t sound like security is the issue…you could make a data field in your application some where that would be ‘link passcode’ then set the privacy to 'get data from url parameter passcode = do search for ‘link passcode’
do you know how to make and send a normal link in an email?
The issue here is, you cannot use “get data from url param” in privacy tab under data section. You can only refer to that “Thing” being used and “Current User”. Or am I missing something?