That macro is deprecated; it's recommended to use "<br>" for inserting
line breaks instead.
However, you could grab the DeprecatedFunctionsPlugin for legacy support:
http://www.tiddlywiki.com/coreplugins.html#DeprecatedFunctionsPlugin
HTH.
-- F.
We'll sort this out with the upcoming relaunch of TiddlyWiki.com.
-- F.