The guilogger is tool to control multiple gnuplot windows and select on the fly what you want to see.
It is called from within the simulator by
-g NTH in the cmd line or
Ctrl+g in the graphical window.
After you check marked you channels you may want to use 'Menu→Save config' to save you selection. You can also edit the guilogger.cfg that is created in your simulation folder to customize the number of windows, window placement etc.
Normally the guilogger plots the last 250 values of a channel. Note the NTH (see cmd line) decides how many points the guilogger gets (NTH = 10 means every 10th). You can also change the reference channel in the reference row by inserting the name. In the screenshot you see two examples.
You can also start the guilogger offline on a logfile with
guilogger -m file -f FILENAME
Then the behavior is changed and you can select ranges you want to plot freely. You can also replay a file to the guilogger (or matrixviz) with
feedfile.pl 25 < LOGFILE | guilogger
feedfile.pl for help.