excalidraw/packages/excalidraw/components/Stack.scss

.excalidraw {
  .Stack {
    --gap: 0;
    display: grid;
    gap: calc(var(--space-factor) * var(--gap));
  }

  .Stack_vertical {
    grid-template-columns: auto;
    grid-auto-flow: row;
    grid-auto-rows: min-content;
  }

  .Stack_horizontal {
    grid-template-rows: auto;
    grid-auto-flow: column;
    grid-auto-columns: min-content;
  }
}