https://blendermarket.com/products/meshmachine

MESHmachine is a blender mesh modeling addon with a focus on hard surface work without subdivision surfaces.  Fuse and Unfuse Surfaces, create Variable Fillets and Washouts, edit and fix Bevel geometry, Unbevel and Unchamfer, create and clean up Boolean Intersections and create perimeter loops, keep earlier mesh states around as Stashes and use them for Normal Transfers, flatten and straighten normals, symmetrize and mirror custom normals, and detail surfaces flawlessly using Plugs - incl. your own custom made ones.