[alwillis]

It's not hidden or undocumented; it's in the man page.

Here's 15-year old HN link about it: http://grack.com/blog/2011/02/23/ssh-escape-sequences-or-don...

[cestith]

Here’s a link to the man page for people who want to read man pages in a browser. https://linux.die.net/man/1/ssh

https://die.net and https://ss64.com are sites I’ve been recommending for years.