Hierarchical Structure/ Outliner/ Tree style Apps

TreeNoote is a brand new note-taking program, free, secure and available in a portable version.

A new medium for your ideas—augment your thinking with a text editor designed for structuring lists. Side-by-side views allow 3 modes of thinking.

Provides infinite text-based nested lists, real-time collaboration, tagging, file uploads, kanban boards, offline access, and seamless sync across devices.

Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.

This program is a structured notetaking application based on GTK+ 3. Write your notes in instantly-formatted Markdown, organise them in a tree of folders that can be instantly navigated from within the program, and add hand-drawn notes by mouse, touchscreen or digitiser.

RunaBook is a tool for creating notes, managing tasks, and establishing knowledge bases. It features a tree-structured record system for easy organization, and offers various field types for data entry, such as text, number, date/time, and labels.

Dendron is an open-source, local-first, markdown-based, note-taking tool built on top of VSCode. It supports all the usual features you would expect like tagging, backlinks, a graph view, split panes, and so forth.

Free, open-source note-taking with rich text, cross-platform support, syntax highlighting, embedded files, and customizable interface.