Since 1.19, you can select entire rows by clicking one row in the left margin of the PE, and even multiple rows by dragging. With MPT 1.20, you can now select an entire CHANNEL by double-clicking in any field in the channel column (if the option is set), BUT you can't select multiple columns by dragging.

What would be great is if you could double-click-and-drag to select more than one column. That is two quick clicks of the mouse, but on the second click (or perhaps third click if implementation on a double-click is problematic), if the user holds the mousebutton down, he can can then drag the mouse to select multiple channels.