This is not possible. You can’t rename the labels Baseline, …, Baseline 10. Your latest baseline should be saved in Baseline, as values stored in this baseline set is used for variance calculation. Baseline 1, …, Baseline 10 is used to store the previous baselines. So, to take a backup/copy of your current baseline, in Set Baseline dialog choose Set Interim Plan with Copy from as Baseline and To as Baseline 1.