KiCad’s drawing capabilities are a bit limited, especially for arcs, but a job like this can be done.
Select the Edge.Cuts layer.
Pcbnew / Place / Draw Arc and then experiment a bit with how the control points work.
Mark the center of your existing arc. The easiest and quickest is to just move it (temporary) to some other layer. This way you have an example of what you want to do.
Draw three arcs. One around the hole, One from the hole to the horizontal line, and the last from the hole to the vertical line. Just draw something that’s close.
Refine your arcs. Drag the manipulation points so they snap together. The final PCB outline must be a closed line.
Delete the arc you moved to another layer. It’s not needed anymore.
Load your footprint in the Footprint editor (With [Ctrl + E]) then delete the right pad, and put the footprint back on the PCB (A neater way is to first put it in a project specific library, and update the footprint link in the schematic).
It’s doable, although a bit finicky.
Another way is to edit your PCB outline in the same program you made it with in the first place, and then re-export it to KiCad. There are measurement tools in KiCad that can help with determining the center of that hole related to other graphical items.
Thank you very much!
I went the second route and altered the outline in the external cad tool (after importing the 3d model from kicad to it). That seemed a bit more easy.
Anyway, it worked as I wanted it to: