I should mention that he wired the jacks so the bridge goes to one jack, the neck to the other. It's more clunky, but doesn't require a TRS cable nor splitter box.When you say merge, which of these do you mean?
A: "standard" mono jack -> amp
B: rick-o-sound -> parallel processing -> summing mixer -> amp
"Rick-O-Sound" into a stereo volume pedal that then sums mono into to the pedalboard vs the split board for each pickup.