If you mean the screen that shows the Create Issue option and the one that pops up when you link issues, not from JIRA. You would need to modify the source code to do that and that leaves you open to any changes Atlassian may make in the future to break your system.
https://confluence.atlassian.com/jira/defining-a-screen-185729487.html
That's the one. It answers my question.
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