So, you want to open your case manager portal and then take your user directly to the favorite tab ? Is my understanding correct ?
If that is your requirement , then you need to modify your portal to have the favorites section appear by default so that whenever anyone opens the portal, they can see the favourites tab as the first one.
I am not aware of any other mechanism which can help you in this. Will do some research at my end and get back you meanwhile please explore the suggested option. .