If you had TWO you could do this.
You set one to In 1, Out A Out B (and run your effects through A for example and leave B empty) and then run the second as In 1 In 2, Out A.
Thus you split your chain into A and B, with A effected and B clean, and then recombine it into one signal. You'd then use the level controls to change the wet/dry mix.
Basically it would be much easier to buy an LS-2 and use one of the mixing modes or a dedicated blender pedal (lots available on the market) than it would be to use these as obviously this method requires two pedals, not one.