So back to Novation Launchpad Mini - while the round buttons are not placed left and right but top and right, they do send the MIDI commands. I keep my Launchpad on the open desk drawer, to the right to my chair, so the right-side column of round buttons works perfectly as the right line select keys. The top row of the round keys is not placed as conveniently, but still, from my perspective when sitting on the chair, they go from top (farthest) to bottom (closest to my sitting position) and can be used as the left column of line select keys.