In FL Studio there are different possibilities to draw automation lines. One is hold. This means you only have to draw one point wherever you want and volume is hold until the next point and than goes straight vertically to the new point.
If I want to do that in Studio one: I have to draw a point and adjust the following point too. Difficult to explain. If my singer sings something more quiet for some seconds, I can't make this duration louder at once. I have to make the first point louder and than there is a line down to the following point. So I have to make the following point louder too. The problem is I want to find the right volume for the whole duration without fiddling around with 2 points.
See in the picture. In FL Studio you only have to draw one point and volume is held to the next point: