Default (Linux).sublime-mousemap

[
    // Mouse 3 column select
    {
        "button": "button3",
        "press_command": "drag_select",
        "press_args": {"by": "columns"}
    },
    {
        "button": "button3", "modifiers": ["ctrl"],
        "press_command": "drag_select",
        "press_args": {"by": "columns", "additive": true}
    },
    {
        "button": "button3", "modifiers": ["alt"],
        "press_command": "drag_select",
        "press_args": {"by": "columns", "subtractive": true}
    }
]