Right now, all navbar links will open in the new tab/window. There is no option to change that. If you need navbar links to open in the same tab/window, use JavaScript snippet provided below.

window.Tribe = {
	onPageChange: function(pathname) {
		var menuItems = document.querySelectorAll(".main-navbar a");
		menuItems.forEach((item) => {
			item.target = "_self";

Go to your admin panel > Theme > Advanced Settings. Copy and paste this snippet inside your "Code added to the end of <body> tag" text box. Save. Then make sure to hit refresh in your browser or CTRL + F5 to reload contents. Without reloading, this new snippet will not be applied.

UPDATED: Code updated with new Tribe JS functions.