It looks like the instructions JMC provided are all in the Task context, so we would be using a quick action from the Task (Assignment) BO which would be used as the 'Add New Task' quick action in JMC's expression.
We can do this by creating a new 'Create Object' BO. When populating the fields, ensure any mandatory fields are set then simply add:
ParentLink_RecID = $(ParentLink_RecID)
ParentLink_Category = $(ParentLink_Category)
We are just telling it to use the current Task values to populate those fields i.e. link it to the same parent.
Hope this is what you were looking for
Errrrm... ignore my last post. That's my bad - I'm an idiot and didn't read properly!!
The QAs run off the Incident object as per the PromptAndExecute (this has a unique syntax for the first parameter)
You should be able to setup everything as per JMCs post, ensuring that the relationship specifier is correct and the named quick actions exist on Incident i.e. Incident#.Rev3 & Resolve Incident / Add New Task
$(IfAllSiblings("Incident#.Rev3", $(Status not in ("Closed", "Resolved")), $(Status in ("Completed", "Cancelled", "Rejected")),
$(PromptAndExecuteAction("$(Parent(Incident#.Rev3))", "This task belongs to an Incident with no other active Tasks. Choose [Yes] to Resolve,
[No] to add a new task, or [Cancel] to go back.", "Resolve Incident", "Add New Task"))))
Because it is running in the Incident context, you do not need to populate the link fields, just any mandatory fields that do not get populated e.g. this worked for me:
As JMC mentioned, you could use a prompt here if you wish too
You wonderful person.