If a Panelist is speaking, the name will appear on the Attendee's screen. You can set it so everyone can see the Attendee list, but you may not want everyone to see everyone's name.
How about a list of Panelists just below the slides or whatever window you are sharing? You could do your PowerPoint show in a window rather than full screen. Then create a document, even Word will work, and position that on your second computer display so that you can see both the PowerPoint show and the list of presenters. then share that entire display with the GoTo audience. You could even include a logo in the corner of the display. Let me know if you need more details about this.