Hi @Stefan Schippers, one question, do you know why when pressing "f" sometimes in xschem the graph is inverted? Is there another key to reverse it again?

the 'f' key does a full zoom in x direction, from low to high. You can manually change the direction of the graph by manually swapping xmin and xmax in the graph dialog box (double click inside the graph to bring it up). If youpress the left button mouse and draw to a different location on the x axis the graph will be zoomed to that x range. If you do the same thing with

Shift

key pressed the zoom will be in reverse direction.