how about this?
looking at this with a sober eye it seams this would be much more handy in matrix view
or not 
Multiple selections at the same time would be great across the whole board, from the instrument list to the mixers volume sliders to the pattern editor content etc. Maybe the same way you can do it in windows explorer selecting multiple files using the mouse in combination with a computer keyboard modifier key? This has been suggested before though and there is a tool regarding the mixer volume sliders (http://www.renoise.com/tools/multi-volumes ), don’t think this’ll make 3.1, but who knows?