Create a series of lines which start more emphasised in size and colour and become less emphasised, with reducing space between each pair of lines.
This technique gives a 3D “plane” effect as seen in the 80s in computer graphics, so it helps if you want to reinforce a theme. It’s relatively simple and not very visually heavy.
You might need to play with the colours, widths, and distances between lines to make sure the “plane” effect is good. This divider also takes up more space than a single line, so keep that in mind for your layout/vertical rhythm.