What is it used for?

The {multi-excerpt} macro allows one to define part of a page as an excerpt to reuse in another page. Very useful when content needs to be seen on several places, to avoid useless duplication and versioning management.
This macro is used by combining two macros.
First macro, {multi-excerpt:name=excerpt-name} is used to define the part of content you want to reuse.

Ex: This content will be reproduced exactly hereunder. You can use any wiki-markup in the multi-excerpt, but you cannot put another excerpt in it. I could hide this excerpt by adding the "hidden" option: {multi-excerpt:name=test|hidden=true}

Second macro, {multi-excerpt-include:spacekey:Page Name|name=excerpt-name} is used to display the excerpt.

Ex: