The DispG screen records all graphic commands since the beginning of the session or the screen was last erased. The Alt+D command (or the menu command Cfg ▸ Show ▸ DispG) brings up this screen.
The erase command clears the DispG screen without restarting the session. The commandline erase or erase() clears the DispG screen. This can be useful for commands such as graph2tex, which only takes into account the objects on the DispG screen.