Preheat oven to 350 degrees F. Butter 4 small loaf pans. Line with parchment paper, butter again and dust with flour, being sure to knock out any additional.
In a large bowl, combine flour, coconut, sugar, baking soda, and salt. Set aside.
In a medium bowl, combine the mashed banana with the yogurt, eggs, butter, and vanilla. Gently add the wet mixture into the dry mixture and stir about 10 times. The batter will be thick and lumpy. Fold in the slivered almonds if using.
In a microwave safe bowl, heat the Nutella for about 15 seconds, stir, and microwave for another 15 to make the Nutella smooth. Set aside.
Divide half of the batter among the 4 prepared pans. Spoon half of the Nutella over the batter filled pans and using a butter knife, swirl the Nutella.
Evenly divide the remaining batter and repeat the Nutella swirl with the remaining Nutella.
Bake for about 25-30 minutes or until a toothpick inserted into the center comes out clean, not including any hot melty Nutella goodness. Cool loaves completely. If using a metal pan, remove from pan after 20 minutes. If disposable pans, just allow the bread to cool in the pans.