I did this Google search: "windows simple outliner" and got this:

http://apps.microsoft.com/windows/en-us/app/simple-outliner/aceb2934-8a84-40cc-8fe5-25c20dfd4c67

a program in the Windows store for 8.1. Has anybody tried it? It looks pretty lean and clean.

Ah, never mind. This is the Diigo product, covered before on this forum.