Some blocks in nTop take in list inputs and combine them into a singular entity. An example of this is the Boolean Union block, which takes in a list of bodies and generates a single unioned body. Blocks like this are auto-populated with an empty list, which is useful for quickly dragging bodies inside to complete the operation, as shown below.
But, sometimes, a user already has a list prepared that they would like to perform a boolean union operation on. In this case, the auto-populated list must be deleted and replaced by the desired list.