The range buttons start, stop, step are a useful way to create many test states efficiently. But it is important to remember that those states still must be processed by the compiler and optimizer. And the actual order of tests is not determinate, even though the button title is "start" and "stop". The optimizer and compiler's default order is from low to high. To sweep in alternate directions or to force arbitrary order, the order must be forced by other means.
A convenient structure to use is the lock step, and with it the inner loop or outer loop object. The two together can force any order desired.
A pair of buttons in a lock step like pictured below will cause the voltage to start at 3 and move down to 1.4, sweeping in a negative direction. Without the "Inner Loop" button, the compiler goes from low to high by default independent of the start and stop values. It is important that the optimizer is ON for the inner loop parameter to be utilized by the optimizer.
In this case the measurement will start at 3V and sweep down to 1.4.