I wouldn’t use the Samsung Connect App at all. It’s going to create bigger issues for you.
Until they migrate all of your ST stuff over to the Samsung account, you will see no devices and I do not recommend that you try adding devices in the Connect app.
Log into ST with your SmartThings account/pw only.
When they are ready, you will run thru the migration process so that all devices transfer to the other account.
The only people that this exists for right now are all the Account Migration Beta users and most of us are not touching the other app until ts ready. Just browsing and comparing functionality. Leave it alone. You will thank me later