:h ctrl-\ in Vim opens the subsection about the mapping of Ctrl-\e in Cmdline mode to evaluate an expression and to replace the command line with the result.
Is Ctrl-\ used for something in other modes too? (I couldn't find anything about this) Even if it is, why is key sequence to evaluate an expression in Cmdline mode not simply Ctrl-\? Are there other key mappings starting with Ctrl-\ in Cmdline mode? Will there be problems if I do
cnoremap <C-\> <C-\>e?