The end offsets in the Part Setup menu add or subtract material the ends in real-time. This is the starting tube with no A End or B End offsets.
We can change the B End Offset in the Part Setup menu like this: Then we press F2 to refresh the graphics, and B end is made longer - without moving the end point.
We can also subtract material from an end by using a negative value like this: Then we press F2 to refresh the graphics, and B end material is made shorter without moving the end point.