As with all Source Editor keyboard shortcuts, you can modify the shortcut assignments for code completion. You can change the shortcut to display the code completion box, and you can create a shortcut to hide the code completion box.
By default, the keyboard shortcuts for opening the code completion box are Ctrl-Spacebar and Ctrl-\. There is no keyboard shortcut already set for Hide Code Completion.
To add a shortcut for code completion:
The shortcuts for the command are displayed in the Shortcuts panel.