Click a slot to edit it. Drag & drop to move items between slots.
Items in the Chest will be put in your inventory in exactly the same order, so put hotbar items there.
Items in the White Shulker Box will be put in your inventory in a randomized order, so put items there that are disorganized during a run.
Items after the chest and shulker box are triggers. Read
this part of the
MiniPracticeKit README
for an explanation.