Custom patterns can be created in RGG with the simple syntax:

class patternName(@In Node a, @Out Node b) (
    // some patterns
    )

Custom patterns requires to declare variable with both annotations @In and @Out. It can be two different variables, or the same one. e.g.

class patternName(@In @Out Node a) ( )

The custom pattern

- context - in and out - open ends - custom nodes - combining - node pattern / edge pattern.

// declaration
class xyzPath(@In Node a, @Out Node b) (
    a -x-> -y-> -z-> b
    )
 
//usage
void rule() [ Node -xyzPath-> Node ==>; ]