The project key comes out everywhere - the issue IDs are keyed on it, it's thrown out whenever you're looking at a project or issue, it's embedded in urls and the rest.
So, no, there's no way to "hide" it really. JIRA effectively stops working if you don't have it, as the users won't really be able to use it at all.
Could you explain what you're trying to achieve though?
I’m a designer on the Jira team. For a long time, I’ve fielded questions from other designers about how they should be using Jira Software with their design team. I’ve also heard feedback from other ...
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