How to add new values to select list field in jira dynamically or using plug-in

[MohammadA]

Here is the my use case.
1. I have a "Customer Name" text field and "All Customers" single select list.
2. When issue is resolved I want to pick value present in "Customer Name" and want to add in "All Customers".

I am able to achieve this If a value to be added is already present in "All Customers". But I want to populate "All Customers" field with new value if it is not present already so that in future it is available for selection. How to do this? is it possible to do so?

[Nic Brough -Adaptavist-]

This is a repeat of a question you already commented on, and has a lot more information.

Please see the answers there, rather than get them repeated here.

https://answers.atlassian.com/questions/192080/adding-items-to-a-custom-field-select-list

[MohammadA]

I wasn't very clear there hence asked a separate question.

I'll put my reply there only.