At this time, Triib does not support split class rates. However, as a workaround, you could set the Coach Payment Override (under Schedule/Classes > Class Types) to the rate each individual coach will receive. Please note that this option only works if both coaches are to receive the same rate for the class.
For example, if you run a class with two coaches, and each coach is to receive $15, set the Coach Payment Override to $15:
Next, go to the class schedule and select the coaches for the class:
Once the class is completed, the "split" pay will be reflected in the Payroll report (Income Reports > Coached Classes (Payroll) as "Specialty Classes."