This page shows representations of a tree structure, in 3 different ways.

The 1st design has sub-items that we display directly under a selected item.

The 2nd design has a visual hints that the items form a sequence, in the form of a line thag goes through the first column.

The 3rd design represents an actual tree, with folders that can be opened of closed, but is otherwise still presented as a grid.

Features such as filters, column settings, selection of a subset, may still be available for these visualizations.