According to the official documentation you can change the key format with a Perl5 regular expression. Unfortunately, this setting cannot be found in my settings. I viewed this with my JIRA admin, who has all rights.
What do I have to do to get my Jira Admin to get this missing setting?
Instructions:
To change the project key format in JIRA Software Cloud to allow underscores, you need to be a JIRA admin and follow these steps:
- Navigate to the JIRA Advanced settings page.
- Find the jira.projectkey.pattern property and click its value to modify it.
- Enter a Perl5 regular expression value that defines the rule for a valid project key1. For example, if you want to allow underscores, you could use a pattern like [A-Z][A-Z0-9_]*.
https://confluence.atlassian.com/adminjiraserver/changing-the-project-key-format-938847081.html