A bit late but I've since found the fix. Seems hero editor is looking for a registry value for "Save Path" but the new blizzard installer doesn't install this value. Fix instructions are:
1. Open Regedit as admin
2. Browse to \HKEY_CURRENT_USER\SOFTWARE\Blizzard Entertainment\Diablo II
3. Add a new value (String Value).
4. Call it "Save Path" and set the value to the location your save files are in eg C:\Users\USERNAME\Saved Games\Diablo II
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Shupershuff - - 1 comments @ Hero Editor V 1.04 - Final
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