A way to do this directly in Orchard Core may be nice, but in the meantime you can do something like this in your code through a shape table provider. This is how I added target='_blank' to certain admin menu items.

public class Shapes : IShapeTableProvider
{
    public void Discover(ShapeTableBuilder builder)
    {
        builder.Describe("NavigationItemLink__admin")
            .OnDisplaying(displaying =>
            {
                string id = displaying.Shape.Id;
                if (id == "some_menu_id")
                {
                    displaying.Shape.Attributes.Add("target", "_blank");
                }
            });
    }
}

Do you mean to add an option for menu items to generate the anchor with target blank?

Do you mean to add an option for menu items to generate the anchor with target blank?

Yes, the menu items of OC support external links, but we can only open them in the current window.

Adding a settings will be useful where users can alternate between _self (default), _blank, _parent, _top

@hyzx86 will you submit a PR for this?

I'm thinking about how to design this interaction...
The average user may be overwhelmed by so many options, and if a predefined drop-down menu is used, it may not be enough for developers