Tab groups with "close existing tabs" unchecked as default

How to set as default the check box "close existing tabs" unchecked for new tab groups? I'd like all new groups with this check box unchecked. Can you help me?

Thanks

I don't think you can.

IMO there should be options in preferences which specify whether the "close everything else" flags are on when saving new Tab Groups and lister Layouts. I've filed a feature request.