During development I always log in to Episerver, open Edit and middle click (open in new tab) on Admin to be able to quickly switch between these to views. You have now made that impossible since there's only a script click event—i.e. not a real anchor element—on these buttons. A right click establishes this quite clear.

Change this back. A button leading to a new url should always be an anchor. Simple as that. Whether or not I should open this new page in the same browser tab or not is not for your developers to decide. Click events like these are just bad practice.