In order to change the contents of the chests, you need to do the following. Take the small chest and place it on the ground, and then place an armor rack called “air_loot” on top. More details are shown in the picture below.
After you create this simple structure, you can put in the chest any items that you would like to see in the Airdrop.
You can also create several chests with different contents at once, which will be randomly selected when supply boxes appear.
Also in the mod it is possible to summon supply boxes yourself using a special device, the recipe for which you can find below. In order to summon a supply box, simply take this setup in your hands and long-tap the screen.