I have a few external drives. Quite a few. OK if I’m completely honest I have hundreds of external drives! In all the years I’ve used a Mac I’ve never had a problem like the one I’ve faced recently.

One of the drives, and only one of them, stubbornly refused to display the disclosure triangles next to each root folder. The disclosure triangles inside all those root folders display quite happily but at root level nothing. No amount of refreshing, unmounting, remounting or other incantations brought them back.

What does that look like? Here you go: First, what it should look like:

Secondly, what I’m seeing:

Eventually, sick of puzzling over it, I deployed my secret research weapon … Mike! As I scoured my settings he scoured Google. Between us we confirmed this was an issue and more importantly deployed a simple solution.

It turns out that up to the release of macOS Sierra it was standard for all folders in any window to have a disclosure triangle. It was from the release of macOS High Sierra strange behaviour was noticed by many. The trouble starts when the View Options are configured to anything other than “none” in List View or Cover Flow view. That setting results in the disclosure triangles unceremoniously vanishing.

How did this option get set differently than every other hard drive I own? I have no idea! Do Apple intend that behaviour? Who knows! However, the solution is a breeze; simply select “none” in View Options.

Sorted!