Stop Creating child issues in Epic when it is already created.

[AM]

I(newbie) have simple workflow which has Statuses ToDo --> In Progress --> Done. when an issuetype Epic (parent issue) is created, it creates 3 stories(child issues) (I used Create A Linked Issue (JSU) to create all the 3 stories automatically when the epic is created only when it is in In-progress transition state.

Scenario 1:
Now the epic is in In-progress state. If I go back to ToDo status and come back to In-Progress status it again creates 3 new stories. 
Q: If I go back to ToDo status and back to In-Progress it should not create 3 new stories, how can we achieve it?? Any suggestion on pre-condition or JQL query?

Scenario 2:
When the Epic is Done. All the 3 stories are done in Epic as well. 
Q: If we go back to ToDo status from Done, then it should not allow to create 3 stories again.

I also checked https://beecom-products.atlassian.net/wiki/spaces/JSU/pages/25680577/JQL+Use+Cases 
it doesn't help me in my scenario but it is similar. 

[Stefan Forstmoser {Appfire}]

You can use the JQL precondition:

"Epic Link" = {issue.key}
Must not find issues

Then in the "Create Linked Issue (JSU)" post function set:

Precondition must be: True

[Brant Schroeder]

@AM 

Welcome to the community.  

Since you are using JSU you can add a Precondition: JQL (JSU) post function before the Create a Linked Issue (JSU) post function and ensure that the JSU is false before creating the issues.  If these additional issues should always be created I would just move them to the issue create transition since it only happens once and this would also elevate the issue.  This would be the easiest to maintain as well.