I have a box that can't be cut from one piece (think: simple cardboard box open at the top).

I modelled the box as a generic Extruded Boss/Base,

then used Shell command, then Convert to Sheet Metal,

then Split (because it can't all be cut from one sheet),

then add Edge Flange around the top perimeter of the box but it needs a miter on the corners so I

add Break Corners.  I want to end up with 4 pieces with a mitered top edge pointing to the inside of the box.  This is what Solidworks gives me:

If I have a single Base Flange/Tab, I can add an Edge Flange and it will break the corners automatically if I simply continue to select the edges, but this doesn't work on a split part with multiple Base Flange/Tab features.