2C-split is an interactive autoloaded compiled Lisp function in `two-column.el'.

It is bound to <f2> s, C-x 6 s.

(2C-split ARG)

Split a two-column text at point, into two buffers in two-column minor mode.
Point becomes the local value of `2C-window-width'. Only lines that
have the ARG same preceding characters at that column get split. The
ARG preceding characters without any leading whitespace become the local
value for `2C-separator'. This way lines that continue across both
columns remain untouched in the first buffer.

This function can be used with a prototype line, to set up things. You
write the first line of each column and then split that line. E.g.:

First column's text sSs Second column's text
/ \
5 character Separator You type M-5 C-x 6 s with the point here.

(See C-h m .)