Can you please tell me how can i update a custom field with Parent Issue key?

[sudheer naga]

Can you please tell me how can i update a custom field with Parent Issue key?

[Nic Brough -Adaptavist-]

Code. You need a post-function or listener to extract the parent key and update your field.

I'd look at the script-runner plugin to enable this, as it saves you having to write an entire plugin.