In BMS firmware 3.X.X, you can reset the baseline by browsing to the System tab on the top of the interface. On the left side of this screen, there is a Reset option to choose. When this is opened, there is a check box where resetting the Charge Current Deviation Benchmark can be selected (see image below). Once this is reset, the unit will initiate the process of establishing a new baseline.
To establish the baseline the system will perform the same test on an hourly basis, repeated until the overall string Delta is less than 3%. Once the string delta is less than 3%, the BMS considers that to be a stable reading, and that data is stored as the baseline for comparison.