Beyond Compare - Beyond Compare allows you to compare files and folders.
Freeplane - Freeplane is a powerful and free software for building mind maps.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
SuperNotecard - Introducing SuperNotecard. SuperNotecard is an online writing tool that features virtual notecards to help arrange facts or scenes, track details, organize paragraphs, and clarify your composition process.