Setting the child boolean argument on a cross reference to a header as in:
\x[my-header]{child}
makes that header show up on the list of extra parents of the child.
This allows a section to have multiple parents, e.g. to include it into multiple categories. For example:
= Animal

== Mammal

=== Bat

=== Cat

== Flying animal

These animals fly:
* \x[bat]{child}

These animals don't fly:
* \x[cat]
would render something like:
= Animal

== Mammal

=== Bat (Parent section: Mammal)
(Tags: Flying animal)

=== Cat (Parent section: Mammal)

== Flying animal (Parent section: Animal)

These animals fly:
* \x[bat]

These animals don't fly:
* \x[cat]
so note how "Bat" has a list of tags including "Flying animal", but Cat does not, due to the child.
This property does not affect how the table of contents is rendered. We could insert elements sections there multiple times, but it has the downside that browser Ctrl + F searches would hit the same thing multiple times on the table of contents, which might make finding things harder.
== My title{id=my-id}

Read this \x[my-id][amazing section].
If the second argument, the content, is not present, it expand to the header title, e.g.:
== My title{id=my-id}

Read this \x[my-id].
is the same as:
== My title{id=my-id}

Read this \x[my-id][My title].
A live demo can be seen at: \x child argument demo.
Generally, a better alternative to this argument is to use \H child argument.

Ancestors