Specify minimum distance between vias/microvias

Had a comment back from PCB fabricator Würth Elektronik: "Please adjust the pitch between plated hole and micro via to min. 400μm". Had to do this manually by placing a 400um radius circle over each via and then moving the microvias. Via-via spacing rules are needed for HDI construction, especially where via-pad + trace clearance + microvia-pad is less than the minimum drill-drill separation required by the PCB fabricator.