If you run a DC simulation and write into the raw file, then do the command

set appendwrite

, run another DC sim and write, run another DC and write, all 3 simulations are saved one after the other in the same file. If you load this data into a graph it shows 3 curves for each waveform, however you can create 3 graphs and each one displaying a different run. After loading waveforms in the graph double click the graph and set a number (0 ... nruns-1) to indicate which run to display in the graph (the

Dataset

textbox). By default all runs are displayed and you see multiple waveforms. Below graph is a cumulated of 100 transient runs. For this to work all dc simulations saved must have the same saved variables. If you change the circuit between one run and the other it will probably change the set of saved nodes and xschem can not load multiple runs of different circuit topologies.