RetopoFlow 3 - Retopology Toolkit for Blender - Blender Market
GitHub - LokiTheCuteBear/RetopoView: A small Blender addon that enables drawing colourful overlays over meshes for user-defined face groups - for marking topology flow during retopology/studying topology.
Quad Remesher auto-retopology add-on released for Blender [$] - BlenderNation