Enable Slickedit style 'Column Selection'. Just highlight using right mouse button instead of left mouse button. Note: If the mouse doesn't move the context menu will still show.
SlickEdit & CodeWright Style Column Select Package
This package borrows most of its functional code from the Sublime Style Column Selection Package.
In SlickEdit and formally CodeWright column selection is performed utilizing just right mouse button and selecting the block of text desired. The benefit of this is that column select is no longer a two handed operation.
As of v1.6.0 you can now hold down control in order to make multiple column selections. Courtesy of purdeaandrei.
Note: I have occasionally noticed this package "going crazy". It looks as if Atom gets into a bad state and some of the information required by the package isn't returned properly, so the selection ends up at a random place on the screen.
Workaround: Use Atom's View->Reload menu option and the package will
function again.
This has now been tested to work under both Windows and Linux, but I have no Mac available to test with.