Editable target x and y fields to place/move targets numerically. I often want to place targets perfectly 1/2, 1/3 way, 1/4 etc between grid lines. Having to rely on eye balling it off grid and making repeated corrections is time consuming. Also knowing that it is slightly imperfect and off by a pixel or two stresses me out more than I want to admit. This would be less critical with custom grid options, but still a nice feature to have and I expect should be fairly easy to implement.
Originally requested by @Zernys in #86