When adding a Calc stage directly connected to another Calc stage, often they belong together and, in hindsight, would have been a MultiCalc instead. Changing to a MultiCalc however, requires copying the Calc properties to the MultiCalc, adding your new calculation to the MultiCalc and removing the 'old' Calc.
Wouldn't it be nice if you could convert a Calc stage to a MultiCalc stage by Right-Clicking it and select where you want it to go?
Obviously, when you have a MultiCalc you might want to convert it to a Calc stage or stages in the same manner.