Favouring SMB and UPnP folders at the same time will make the SMBs ones go missing on next start

As long as you don't restart, you'll see both servers listed in the Favourites tab. On restart, only the UPnP section will show. However, when browsing the SMB share, it will be apparent that the favourites are still indicated.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information