Hi,
Sorry, CTRL+Space is reserved for auto-complete and even if you turn it off, there is a limitation assigning the space key to a shortcut.
I would recommend using another shortcut.
FYI, auto complete lists the words used in the document making it easy to reuse them. optionally folders and files of the same folder as the original document are displayed as well, useful for editing web documents like HTML or CSS.
Thanks,
André Santos Carthago Software Support
http://www.carthagosoft.net