In a large bowl, combine the wakame, agar agar, and hijiki and cover with 4 cups cold water. Let stand for 15 minutes to hydrate and then drain. Spread the seaweeds out on paper towels, press to dry thoroughly, and then return to the bowl. Add 2 teaspoons rice vinegar, along with the miso, palm sugar, soy sauce, ginger, and sesame oil and toss to combine. Cover with plastic wrap and let seaweeds marinate in the refrigerator for at least 1 hour.
Meanwhile, heat a 12-inch nonstick skillet over medium-high. Add the macadamia nuts and cook, stirring, until toasted, about 2 minutes. Transfer the nuts to a bowl and return the skillet to the heat. Working in batches, add the nori sheets to the skillet and cook, flipping once, until toasted and fragrant, 10 to 15 seconds. Transfer the nori sheets to paper towels and return the skillet to the heat.
Add the mushrooms to the skillet and cook, stirring occasionally, until their moisture evaporates and they begin to caramelize, about 8 minutes. Stir in the kecap manis and then remove from the heat and let the mushrooms cool.
In a small saucepan, combine the rice with 1 1⁄2 cups water and bring to a boil. Reduce the heat to low and cook the rice, covered, until tender, 15 minutes. Remove the pan from the heat and let stand, covered, for 10 minutes. Uncover the rice and scrape into a medium bowl. Add the remaining 1⁄4 cup rice vinegar, the salt, and sugar and toss to combine.
To serve, divide the rice among 4 serving bowls and then arrange the marinated seaweeds and mushrooms in separate piles next to the rice. Using a paring knife, peel the pith away from the oranges and then cut in between the membranes to release the orange segments. Garnish the rice bowls with the orange segments and then tuck the toasted nori sheets into the bowls. Sprinkle with the macadamia nuts and serve immediately.