The grammar element for a custom condition must have a special id: the prefix condition- followed by the condition’s name as specified in scenarioManager.xml. The optional <element-icon> tag may be used to provide an icon (specified as a class loader resource path). For instance, if you were defining an expression for the custom event MyCondition, you would define the event in the grammar as follows:

<sequence id="condition-MyCondition">
  <element-icon>icon-resource-path</element-icon>
  ...
</sequence>