Develop add Symmetry on 2D UV mapping for texture painting

This is such a frustrating issue that I decided to ask you to develop Symmetry. I saw on YouTube that Substance Painter allows you to paint symmetry UV mapping. That would be much easier than asymmetry. In 3D model painting, you can draw Symmetry, but not in flattened image maps. Why didn't we think of that? I'd appreciate it if you developed this.