> backslash isn’t bound to anything by default Actually it is. That thing is called "leader" and is used exactly for the same purpose as author uses backslash.

> backslash isn’t bound to anything by default Actually it is. That thing is called "leader" and is used exactly for the same purpose as author uses backslash. So better way to write :nmap \o :set paste!<CR> would be :nmap <leader>o :set paste!<CR> Reasons to use "leader" are discussed more than once, so I'll leave reading the docs/blogposts to you.