Using the "loopcut" function first, is there a way to widen the gap between the lines?
I think it's going to happen with "Scale". It's only increasing in volume. :.-(
You can indeed do what you want with Scale, you just need to lock the transformation to the X axis to prevent any transformation on the Y and Z axes. Press S followed immediately by X to lock the transformation to the X axis, and only the spacing between the edges will be modified.
enable symmetry in one axis. For example "X" axis
alt + select clicking on the loop to select the loop
Press the G + X to lock to X and only move in the X axis.
You can now resize the loops in the way you want.