Modeler Extension Elements

Flowable Engine
1

Hello everyone, can i ask where can I found the documentation related to modeler extension elements
For example

<userTask id="sid-D092143E-550B-4C7B-91DD-EA419AD3FCB1" name="Create Ticket" flowable:assignee="$INITIATOR" flowable:formKey="ticket-form">
      <extensionElements>
        <modeler:initiator-can-complete xmlns:modeler="http://flowable.org/modeler"><![CDATA[true]]></modeler:initiator-can-complete>
      </extensionElements>
    </userTask>

what is the purpose of
<modeler:initiator-can-complete xmlns:modeler="http://flowable.org/modeler"><![CDATA[true]]></modeler:initiator-can-complete>

I have searched the definition of this for days but got no luck