How can I unlock the Configuration of custom fields

[Jessica Dahm]

Why is the configuration of some fields e.g.  "Sprint" locked by Jira and how can I unlock those fields again? Because in the old issues it's there and only in the newly created ones I can't add this field. 

[Nic Brough -Adaptavist-]

Your code needs to perform REST calls, we can't help you with that, as you could be doing anything.

But the calls it needs to make to JIRA are pretty standard.  Start at https://developer.atlassian.com/jiradev/jira-apis/jira-rest-apis to get a feel for them.