The command palette can split the current pane up, down, left, or right. Each pane is its own folder.

Tab moves to the next pane. Shift + Tab moves to the previous one. Those keys do this only while the window is split; otherwise Tab stays with the focused control.

The palette labels are Split pane, split: down, up, right, and left. Focus Next Pane and Focus Previous Pane appear in the palette only while the window is split.