However, if the highlighting is lost, you can still use Ctrl-u to  
erase the contents of the Command area.  Ctrl-u erases the command  
line contents, Ctrl-p switches to the previous command, and Ctrl-n  
switches to the next command; further text-editing shortcuts are  
system-dependent:
<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/keys.html#textedit>