Following plugins are available for Cinema 4D R16 – R20, Windows and macOS
Seamilar is a dedicated UV editor plugin. It provides a custom UV editor window, UV editing tools as well as a custom seam creation tool.
PolyGnome allows constructing a 3D model by seamlessly adding mesh details by means of replacing selected polygons from the source mesh with specifically prepared assets.
Dials allows you to set up a list of most used tools, commands, scripts … and more. These are presented as a circular palette to select from. Directly available from the viewport.
EasyUV is based on my Seamilar plugin, but as a younger sibling with less features.
It mainly focuses on the ease of unwrapping UVs, using the specifically created Seam Tool.