On the Microsoft Edge team, we're introducing a new way to draw separators between items of a grid, flexbox, or multicolumn layout. We think it overcomes a lot of the limitations of existing techniques, and we would love to hear your feedback to help us shape the final design.

https://blogs.windows.com/msedgedev/2025/03/19/minding-the-gaps-a-new-way-to-draw-separators-in-css/