Yeah it's a lot easier using a DPDT switch for an added diode mod.
So since D1 already has its anode to ground and the cathode to signal (check the schematic) you don't need a wire going to a ground pad. Also it's called a diode "lift" because it's no longer connected to ground or is now "lifted" above ground. so you do nothing to the other side of the switch. So it kind of looks like this. If we're getting nitpicky you should also switch the red wires around to correspond with how you have the diodes connected there.
Alternatively you can use an on/off/on switch and put some other diodes on the other side, giving you normal diodes/lift/new diodes as your options.