Best practices
Use a table instead of an outline view to present data that’s not hierarchical.
Expose data hierarchy in the first column only.
Use descriptive column headings to provide context.
Consider letting people click column headings to sort an outline view.
Let people resize columns.
Make it easy for people to expand or collapse nested containers.
Retain people’s expansion choices.
Consider using alternating row colors in multi-column outline views.
Let people edit data if it makes sense in your app.
Consider using a centered ellipsis to truncate cell text instead of clipping it.
Consider offering a search field to help people find values quickly in a lengthy outline view.
For the complete guidance, including worked examples and illustrations, see the canonical page: https://developer.apple.com/design/human-interface-guidelines/outline-views