Remembered that I have used the extremly versatile but GUI-wise crazy software called Audioterm.
Finde the Video of how to export a wavetable to Serum Format:
How do you come to have a Wavetable which you can export? Watch the whole series of videos: https://www.youtube.com/playlist?list=PL9KNk-UUudH2Wa3dQdKIkFcM02mWVVaIG
I have used it in the past on some occasions…
] Peter:H [