Subject says it all...
If you set up a favourites list on a portal, it will be on just that one portal.
Correct. This is also true for parental control settings and other customization options.
I think that you can use the gateway app to sync favorites and some of the other settings to every portal that you own
that is correct
The Gateway Portal app allows you to push/pull settings to and from the App.
Retrieving data ...