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Generally speaking, the local settings of UWP apps like fonts, colors, could be saved in LocalSettings. And if the customer wants to share the setting data between different devices, RoamingSettings could help. I'm not sure where you save the setting data in your app. Do you save it in a local file or in some other ways?
Also, I'm a little confused about why you want to enable sharing setting data between users?
It might be better to have a server that could save the setting data if you want to share the setting data between different users. You could upload the setting data to the server and download it according to different requirements.