By default, the skimmer displays stations that are operating in Run mode. I don't think anyone in the pileup is operating in this mode.
You can configure the skimmer to display callsigns in the processing area of function 599. To do this, check the "Spotting only Pile-Up" box in the settings for this function.
But I don't see the point in this, because behind this forest of callsigns on the panorama, you may not see the "599" icon, which is more important.