'Build Sublists' offers a way to customize how a list can be parsed into nested sublists using a parsing syntax.
Example 1... the syntax "0..1" means to get items 0-1 from the list... the offset input tells the node to repeat the same operation 2 items further down the list. The node will then iterate over the entire sequence.
Example 2... the syntax "0..a" will create an additional Node input for variable a so you can control the parsing with other nodes.