command-line-expand-mode

command-line-expand-mode: C-x C-e grows the one-row : line into a multi-line band for editing a long command comfortably.

Press <C-x><C-e> in the : line and the single row grows into a multi-line band. This mode takes over as the buffer's major for the duration.

It's for the commands that don't fit: a long :g/pattern/normal ..., a substitution with a dense regex, anything you want to see while you edit it rather than scroll horizontally through.

Chords

Its own option stack

While expanded, the band gets its own options — no line numbers, no sign column — rather than inheriting the document's. That's why swapping the major mode is the mechanism: the expanded band is visually a different surface from both the one-row : line and the document behind it, and giving it its own mode is what keeps those three from leaking settings into each other.

Everything else about the : line is unchanged: same history, same completion, same parsing. Expanding changes how much you can see, not what you can do.

See also

• command-line-mode — the one-row : line.
• ex-commands — what you can type in it.