The default configuration of URL’s in the Database is to open in a new tab
How can I configure them to open in the same tab?
Opening in the same tab is determined by the browser. This means that it’s very difficult (or impossible) to create a full consistent user experience since different browsers behave differently, and users tend to configure according to personal preferences (where it’s possible to set).
i can see that its defined by WIX
please see screenshot
Aha! Thanks for the screenshot. Now I understand what you’re referring to. This is not a Wix Code issue, rather it’s Content Manager issue.
For questions regarding the Wix Content Manager, please contact the Wix support team , as they’ll know best how to assist you.
Yisrael
I asked the support team first
they sent me here
Perhaps they misunderstood as I did at first. Make sure you show them the screenshot of the problem. This is a behavior of the Content Manager and really isn’t connected with code. I’m not aware of any settings or configurations to change this and they should “know it all”. 
What was the solution to this question?
Hi All - Was there ever a resolution to this requirement? @bestsite-israel did you manage to get this changed?
Alternatively anyone know of a way to stop the wix event external registration link from opening in a separate browser window ?
Jon, you too would be much better suited going through Wix Support as Wix Events is a Wix app and you can’t change that setting, hence why it clearly states on a different page.
https://support.wix.com/en/article/redirecting-event-guests-to-a-different-site-for-registration