I did some tests with multi-threading in blender 2.82 and want to share my discoveries.
cycles rendering. Multi-threaded. (viewport was tested)
cycles rendering with animation is Multi-threaded. (viewport was tested)
Eevee rendering is not multi-threaded when doing animation. (viewport was tested)
Eevee without rendering is multi-threaded when doing animations. (fast and smooth)
Vertice editing is not multi-threaded. Scaling, moving and proportional editing is single threaded.
All sculpting tools are multi-threaded.
Some dynotop functions are single threaded. such as symmetrize.