The principle is easy. You state which concentration of solvent B/C/D you want at a given time point (A =100% -B - C- D) and the system will move there linearly from the previous time point. Hence for a plateau, you need to put the same concentration twice and for a steep step you need to choose two time points that are as close to each other as possible.

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A=100%-B-C-D always (it is an equation), i.e. in Pump tab: B=C=D=0 and A=100% by default.

Ex. If B=20% A goes automatically to 80%.