Xournal++ is a handwriting notetaking software with PDF annotation support. Written in C++ with GTK3, supporting Linux (e.g. Ubuntu, Debian, Arch, SUSE), macOS and Windows 10. Supports pen input from devices such as Wacom Tablets.
Qt5 suite that supports displaying and editing nodes in a graph-like flow. Similar to Unreal Kismet, Frostbite 3 Schematics or Allegorithmic Substance Designer UIs.