ThoughtStack

Designed as a simple notetaking solution for tracking tasks and various ideas, ThoughtStack is a rather approachable tool written in Java which comprises features for organizing information in hierarchical form.
Although the app hasn't been updated for a while, it's worth considering if you're looking for something uncomplicated to keep track of your train of thought in a digital environment. It's not the most intuitive text editor we've seen, but after taking the GUI for a spin for a couple of items, you should figure it out easily.

No setup necessary, besides Java

Provided that you have Java installed on your PC, you don't need to set up anything else. This means that you can drop ThoughtStack anywhere on the disk or on a removable storage unit, and just click its file to launch the app on any PC. It doesn't create new registry keys.

Write and manage notes

In the main application window you can write or paste text and add it to the hierarchical view by creating nodes, edit information and change the node order in the list, zoom in and out, as well as export the entire stream to plain text, FBML (Facebook Markup Language) unordered lists, or HTML ordered or unordered lists.
Multiple tabs are supported, and you can seamlessly navigate them. Plus, you can resort to a basic search function when dealing with large amounts of information, load streams from external files, as well as undo and redo your actions.

Evaluation and conclusion

The program supports keyboard shortcuts and left a small footprint on system resources in our tests. It didn't freeze, crash or display error messages. On the other hand, it hasn't been updated for a pretty long time, and we've noticed that it doesn't work with newer Java editions.
Otherwise, ThoughtStack sports basic options for quickly writing notes and keeping them organized in different categories, and it can be handled by first-time users who prefer a straightforward word processor with standard options only.