KiCad is a wonderful software for PCB designing, it is open-source and can handle the complete workflow from the schematic to the final layout.
Unfortunately, it is not (yet) intended for RF circuit and antenna design. In these cases, a suitable program should be used, which could be ADS, CST, HFSS, or others. These are expensive but, unfortunately, the open-source tools are still not complete enough. I generally use multiple open-source tools depending of the requirements and quite often compare the results to evaluate the correctness.
Long story short, I was facing with the need to create a PCB by incorporating some custom Inductive Power Transfer coils, which I could export to a Gerber file from CST and some patch antennas and matching circuits, from ADS. The idea was to import the different parts from the Gerbers into different footprints, which are then assigned to schematics blocks and placed on the PCB.
There are no ways (yet) to get it simply by using some pre-baked functions, but some tricks are needed.
This post is a walk-through different options that can be used. I try to compare the options and outline the strengths of each one.
Notice that the same methods can be used to produce custom logos or any custom shape.