What I do for arced traces:
- In your layout (Pcbnew), use the graphic arc tool to make your trace with a graphical line, pretending to connect two straight traces or two pads.
- I then view the parameters of the arc and note down all dimensions like angles and position.
- In footprint editor, make a new footprint with a graphical arc with the same exact parameters and change it’s layer to top/bottom copper.
- Import the footprint into Pcbnew. Now, you could either edit the footprint beforehand with SMD pads 1 and 2 in both ends, but then you have to include it as a part in your schematic/netlist. What I do instead is just to lay down the new arced footprint where it should go, and route a thinner “invisible” trace behind it (this will be somewhat staggered, but hidden), leaving the arced footprint unconnected.