Prepare a charcoal fire using about 6 pounds of charcoal briquettes; let burn until coals are completely covered with a thin coating of light gray ash, 20 to 30 minutes. Spread the coals evenly over grill bottom; place grate on grill, and heat until hot. (It is hot when you can hold your hand 5 inches above the grill surface for no longer than 3 or 4 seconds.) Or preheat a gas grill to high (450°F to 550°F).
Combine chicken, sausage, tomatoes, okra, onion, bell pepper, and poblano in a large bowl. Add oil and 2 teaspoons of the Creole seasoning, and toss to coat. Thread chicken, sausage, tomatoes, and okra, separately, onto 10-inch metal skewers. Thread bell pepper and poblano onto a 10-inch skewer. (You will end up with a skewer of chicken, a skewer of sausage, etc. The onions will go directly on the grill. You can use a metal grilling basket instead of skewers for the vegetables.)
Place chicken on grate over hottest part of grill; arrange sausage over slightly cooler heat. Arrange onions and the skewered vegetables at the edges of the grill. Grill, uncovered, turning once or twice, until chicken juices run clear and chicken is done, the sausage is heated through, and the vegetables are tender and slightly charred, 8 to 10 minutes. Remove meat and vegetables from skewers, and transfer with onion to a large bowl.
Add ketchup and scallions to grilled mixture in bowl, and toss together. Immediately cover tightly with plastic wrap or aluminum foil, and let stand until vegetables are slightly wilted, about 5 minutes. Remove plastic wrap from bowl. Stir to combine; sprinkle with remaining 1 teaspoon Creole seasoning and, if desired, hot sauce.