left-click the y-legend , set manually the Top , Tick , Bottom
right-click the plot plane , select (by left-click) the Add Trace , (for your case) 6A, AND the same way -6A
in case there are some startup fluctuations change your I(R1) (← right-click on it to edit the) formula to uramp(6-(uramp(6-(I(R1)))-6))-6 where 6 sets the ±clipping points