In the older version of SignCAD (32-bit) the .sgn files can be opened in multiple windows, but the newer 64-bit versions do not allow it anymore, by design.

If you have to create multiple signs with similar specs it is more convenient to have these .sgn files opened in multiple windows (to compare them on monitor and mass edit them).

Hopefully Bentley will consider giving user the flexibility to either dock the .sgn under tab or open it in a separate window.