Found in the Tools Menu, Sync User Defined Products forces re-synchronization of your UDPs.
UDPs are synched every time Stardraw Design 7.3 runs, assuming you have an internet connection and your Subscription is current so you will rarely, if ever, need to manually synch UDPs.
Use the Sync User Defined Products command if you want to re-synch after Stardraw Design 7.3 has started, e.g. if a user working with the same account but on an different computer has just created a new UDP that you want to use locally.