Gorm has a hardly usable keyboard modifier selection to drag and extend an NSMatrix.
Ctrl-alt-shift is not only hard to remember but doesn't work on any computer.
Perhaps right-alt would work, but it  is not available on many non-US keyboards, like Italian or German keyboards or some laptops anyway.

I suggest to use the same modifier as IB which is "option-drag".

If the used windowmanager "steals" that combination, the user should reconfigure his WM.

Adding an inspector as  discussed privately may be interesting too, but getting the modifier right is easier and also conversant