In Jira Service Management Cloud, it is possible to change a project key (under Project settings > Details). However, it is not possible to use a used project key.

Current Behavior:

• Let's say user has renamed a project key from "ABC" to "KLM"
• Although there is no project uses the project key ABC, user is not allowed to re-use "ABC" for the new project key.

Suggested behavior:

• Ideally, user should be able to re-use the project key "ABC" for other/new project