question

You're on the right path using the "Arrival Table" experiment variable. The next step would be to create two new Global Tables in your model (one for each of your two scenarios you have created in your Simulation Experiment Control window). These global tables need to have the same format as the actual Custom Arrivals table, so a good way to ensure this is to copy one of your Custom Arrival tables (CTRL-C) and pasting it into the global table (CTRL-V). To ensure you have selected the entire table to copy, simply click in the very top left gray square of the table. The last step is to simply write the name of each global table into the Scenario columns of the Scenario table of the Simulation Experiment Control window. You do not need to put quotation marks around the names, just write the name itself.

Let me know if you have any questions.

Another approach some people use, is to create additional arrival objects in their model with each arrival object set up with a different arrival pattern they want to experiment with. Then it's simply a matter of toggling on/off the arrival using the "Activate or Deactivate Arrival Table" experiment variable option. This is analogous to checking or unchecking the "Activate ... ..." box in Quick Properties for an arrival object.