@SYNTAX:layout@

Saves the current window layout to configuration (yes, you'll still
need to use /SAVE to save the configuration to file). Next time you run
irssi, all the channels and queries are exactly in the same windows
where they were when you called /LAYOUT SAVE.

Channels aren't actually joined in those windows immediately, they're
just marked "next time you join to '#channel' in server that has tag
'ircnet' place it to this window".

/LAYOUT RESET removes the saved layout.