Not sure how I feel about this. On one hand, genius. More control for the user is something I’m a fan of. The UX is simple, though not sure how obvious the circle vs square is (the triangle for new tab is perfect). If the link is staying in the same window, it could appear normally with no marking, indicating it’s tied to that window. I would get rid of the square completely and use the circle as the new window marker. Just my $0.02. I’m going to try this in one of my apps and see how it’s received! Great write-up.