Didn’t looked int the video but i discovered this one UV Tool Suite for Blender (A set of tools to make editing UVs easier in Blender.) a few days ago while searching for something else… luckily i bookmarked it but didn’t look to dep intoit (like hundreds of others).
These tools can be accessed wither through the Kitfox - UV panel on the right of the 3D Viewport. You can also access them from the uv unwrap menu…