Welcome to the Finale 3D forum!
As you discovered, Finale 3D currently has a hard limit of 120 seconds for cakes.
As a workaround, you’ll need to make the cake in two parts and then put them back-to-back on the timeline. In order to have the cake parts treated as a single effect for addressing purposes, you can select both parts of the cake on the timeline and go to Script > Chains > Combine as chain. This fuses cake parts together and ensures that only one rail and pin will be assigned when you address your show.
