On the Mac, I highly recommend OmniOutliner. I have outlines that have evolved over, literally, decades. Before using OmniOutliner, I used More, an early Mac ou

On the Mac, I highly recommend OmniOutliner. I have outlines that have evolved over, literally, decades. Before using OmniOutliner, I used More, an early Mac outliner that ran on a Mac Plus. OmniOutliner could import More files[1], so, when More was discontinued, I could keep using my outlines without a hitch. I am still actively evolving and growing outlines today that I may been working with, literally, for 40 years or even a bit longer! I love the process of working with outlines. They're the perfect way to store information in an organized way. There's a common outline storage format, OPML (Outline Processor Martup Language), which OmniOutliner exports to. So, if the Mac ever entirely disappears, or OmniOutliner's publisher (OmniGroup) goes out of business, you should be able to keep using your OO outlines on whatever platform you move to next. Also, OmniOutliner does run on the iPad today. One tip which is key to my own use: use hashtags so that you can instantaneously find the outline heading for whatever notes you're looking for. [1] https://discourse.omnigroup.com/t/does-omnioutliner-import-more-files/24833/2 https://discourse.omnigroup.com/t/does-omnioutliner-import-m...