Column selection

ID Edit.ToggleColumnSelection
Menu Edit→Selection→Column Mode
Default Shortcut Alt+C

The column selection is supported by most of the common actions, which executed with normal selection (Copy, Paste, Indent, ..).

Column selection of text

If you do the selection in Column mode, your changes are applied for all lines.

So you get some kind of mass editing tool if you type or paste char it is duplicated in all selected lines. If you delete a char, it is deleted in the same position though all lines.