The MixingLink can take the line level signal of the Yamaha mixer’s FX Send and convert it to high impedance for you. I would put the wah and synth in the MixingLink’s loop. Take the output of the MixingLink back to the Yamaha’s FX return. Make sure the MixingLink’s output is set to line level with the dip switch on the bottom of the pedal.
Another thing you must pay attention to is whether or not you’re mixing the signal from the accordion with the affected signal of the wah and synth at the same time. This may be causing undesired effects. Remember, you’re running the according through an SY200, a digital effect that will induce latency that when mixed with the original dry signal may cause comb filtering mainly if the effect is not set to 100% wet.
