Toast tortillas directly on the oven racks ( no sheet pan) until crisp, about 20 minutes. This is key- they need to be very crispy and dry, not bendy. You can make these ahead.
Combine the cabbage, carrots, radish, onion, and toss in a large bowl with the salt. ( This will seem like a LOT at first, but will it will release liquid and shrink down.)
Add the cucumber, jalapeño, scallions and cilantro, Toss well, then add olive oil and lime juice and a little zest. Let it rest on the counter – or make this ahead and refrigerate.
If making the avocado sauce- make this now- placing everything in a food processor and blending until smooth. Taste, adjust salt and spice level adding more jalapeño if needed. Place in a bowl.
When ready to assemble, heat the refried beans, adding salt,seasoning with cumin and coriander if you want. If using chicken, heat it up now.
To assemble Carefully later up the beans on the tortilla. At this point you could add the chicken and cheese- or leave it off and keep it vegan. Top with a generous mound of slaw. Spoon over avocado sauce( or sliced avocado).
Garnish with cilantro sprigs, hot sauce, lime wedge, pickled onions or shallots. Serve immediately (with knife and fork) while the beans are warm and the tortillas are still crisp.