Just playing - draw a rectangle then a separate circle - drag the centre of the circle over a corner & the centre lactches to the corner & the two are associated - drag the edge & the circle moves.
How do you break this association? Delete & redraw?
For Inventor Fusion on Mac, this is not as easy as it should be. You need to delete one of the two sketch elements. You can not delete coincidnet constraints directly. This will be much easier in a future update the the technology preview.
15" Macbook Pro Retina - OSX 10.9 in Portland, Oregon