This article explains on how to create new issues only for newly selected custom field values during repetitive transitions.

Step-by-step guide:

1. Log into Jira as a Jira Administrator and click  > Issues  > Projects
2. Navigate to the intended project and Click on Project Settings > Click on target Workflow
3. Click on target transition add "Create Issue"  Post Function. 
4. Click on Conditions and Configurations.
5. Add below JQL query and JQL query returns issue that are linked to original issue with custom field value A.

     6. Add below conditions in Conditions tab and transition will be executed only when conditions are true

      7. Set Custom Field value to A in Custom fields section.

      8. Update the Post- Function and Sample Post functions looks like below

      9. Repeat the steps 3 to 8 for each value of custom field and Sample post functions looks like below.

      10. Publish the workflow before executing the transition. You will be able to see that issues will be created for only new selected value of custom field during repetitive transitions.