Here is a simple guide on how to find all collectibles with images and brief descriptions.
Mago The Villain’s Burger All Collectible Locations
1-1
Visible. Jump or double-jump off the bird from the right, using magic to stun it if necessary.
1-2
Visible. After both donuts, there will be a split path, and a platform to jump up to.
1-3
Hidden. In the water before and under the checkpoint, there will be an inset wall. This is destructible; hit it with your magic.
1-4
Hidden. During an upwards climb with multiple vine platforms, there is a breakable wall on the left. Behind this wall is a donut, and another breakable wall. Behind this wall is a treasure chest, and another breakable wall. Behind this wall is the collectible.
Thanks to Gaphodil for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.