Interesting side-note: the Notebooks app handles OmniOutliner files as read-only, and you can open or close a document's embedded disclosure triangles. Unfortunately it does not allow viewing of OPML files.

It looks like Notebooks on macOS is using whatever QuickLook generator is installed for displaying .oo3 or .ooutline or .opml files -- Notebooks is showing the same preview as Finder. The .opml QuickLook on my machine is not great -- treats indented rows as heading levels for some reason. On iOS no joy at all, in line with @satis' findings.

Paul Korm wrote:

It looks like Notebooks on macOS is using whatever QuickLook generator
is installed for displaying .oo3 or .ooutline or .opml files --
Notebooks is showing the same preview as Finder. The .opml
QuickLook on my machine is not great -- treats indented rows as heading
levels for some reason.

Ah.

I'm curious - QuickLook on your Mac is able to look into .opml files? My Mojave iMac doesn't (which is why it doesn't on Notebooks either, it seems). Do you have a 3rd-party plugin installed that gives that functionality (I have one, for example, which lets you QuickLook into .zip archives), or should it work on my Mac too?

It does. Not very well though. I suppose some app installed the QL generator for .opml or maybe .xml (they are related). It wasn’t something I installed myself.

satis wrote:.

I'm curious - QuickLook on your Mac is able to look into .opml files? My
Mojave iMac doesn't (which is why it doesn't on Notebooks either, it
seems). Do you have a 3rd-party plugin installed that gives that
functionality (I have one, for example, which lets you QuickLook into
.zip archives), or should it work on my Mac too?

Ok thanks. I'm going to have to google around. If you find a plugin that allows QuickLook of .opml please post the name.

FYI, my 3rd-party .zip plugin (in Computer > Library > QuickLook) is BetterZipQL.qlgenerator . Free download:

https://macitbetter.com/BetterZip-Quick-Look-Generator/

Check Fletcher Penny's repo on GitHub. There’s an old OPML QL gen there. Makes me think the one I have was installed a long time ago by MMD Composer.

I have covered Notebooks a bit at https://appademic.tech (mainly on iOS). Alfons is one of the more approachable and responisive developers I have come across, if you're commited to using Notebooks and would like to see functionality added, drop him a line. If nothing else, I'm sure he will happily shed light on how this works.