You can see a list of effect modules (in order) using ~dirt.modules, and reorder them using
~dirt.orderModules([\shape,\vowel])
new module order: [ sound, shape, vowel, hpf, bpf, crush, coarse, lpf, pshift, envelope, grenvelo, tremolo, phaser, waveloss, squiz, fshift, triode, krush, octer, ring, distort, spectral-delay, spectral-freeze, spectral-comb, spectral-smear, spectral-scram, spectral-binshift, spectral-hbrick, spectral-lbrick, spectral-conformer, spectral-enhance, dj-filter, out_to, map_from ]
where you don't have to specify the full list to reorder.
I think all of the "local" effects operate on all channels independently (what you call "monophonic").
If I remember correctly, global effects are effectively in parallel - they each get the "dry" signal and modify it. I think the only one that truly mixes different channels is "leslie".