Is that Sublime Text, Atom, or Brackets? Sublime Text has great multicolumn (and grid) support, but I don't use the others.
Although, if you use a tiling window manager and use lightweight non-single-window IDE/editors, you can just launch multiple windows and your window manager can do the rest. Multi-columns seems like a more natural job for window managers, so editors should be designed to naturally handle multiple windows and be able to quickly close and open them.
Although, if you use a tiling window manager and use lightweight non-single-window IDE/editors, you can just launch multiple windows and your window manager can do the rest. Multi-columns seems like a more natural job for window managers, so editors should be designed to naturally handle multiple windows and be able to quickly close and open them.