Seco has introduced the Square-Six cutter which is a high feed mill with a 90 degree square corner.
https://www.secotools.com/article/m_6920
While MillMax compensates for the lead angle of 45 degree and high feed milling cutters, the Square-Six is a sepcial case. Refer back to our original Special High Feed material database and use it. If it is not in your dropdown menu, you can download it below and add it to you Database Folder on the opening popup menu. Be sure to select the database firts then select or reselect the material.