This menu is active only when a guider or finder camera is defined in CCDciel.
The two options are:
Single Panel to show each camera in the full image area depending on the tab selected on the right. This is the default.
Multiple panel to show up to three camera at the same time in the image area. It is possible to move the slider to adjust each camera size. The main camera is show at the bottom, the guider and finder camera share the top.
This is specifically useful when working with the spectroscope.