how can i create custom field with script runner ?

[Alexander_Sergeevich_Denisenko]

My epics contain the system field Rank, How can I add this field to the tasks of my epik using the script runner or other tools ?

[Nic Brough -Adaptavist-]

I have to apologise for my response to this question, because I think I am missing something, but my attempt to try to clarify what I need to ask may be very unclear.

What is the difference between the issue types of Epic and Epik?