Not for me with Custom Shortcuts it isn't. Using gnome-control-center 1:3.3.92-0ubuntu4 on Precise:
System Settings > Keyboard > Shortcuts > Custom Shortcuts
Click + and enter name and command, Apply.
The prompt at the bottom says to click a row and press keys. Clicking a row pops up the command dialog again. To enter shortcut it is necessary to click at the right hand end of the highlight.
Not for me with Custom Shortcuts it isn't. Using gnome-control- center 1:3.3.92-0ubuntu4 on Precise:
System Settings > Keyboard > Shortcuts > Custom Shortcuts
Click + and enter name and command, Apply.
The prompt at the bottom says to click a row and press keys. Clicking a row pops up the command dialog again. To enter shortcut it is necessary to click at the right hand end of the highlight.