HI Fredrik,
I have seen my mistake when I have re-read the full thread Now it is working. But if you create the links, it will work until your NAS reboot (until the udev process restart).
In order to make it more persistent you have to create a file (udev rules). I have created the file /lib/udev/rules.d/59-usb-serial.rules
I have added the 2 lines for my zwave USB key and for my RFX433 USB device:
SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", SYMLINK+="serial/by-id/usb-RFXCOM_RFXtrx433_A1YHLM21-if00-port0"
SUBSYSTEM=="tty", ATTRS{idVendor}=="0658", ATTRS{idProduct}=="0200", SYMLINK+="serial/by-id/usb-0658_USBDevice_ffffffd1ffffffb2ffffffdbffffffad-if00"
After a reboot, the links were recreated with the good devices associated to it.
the idVendor and the idProduct could be different (depending of our USB devices). I have used the link https://www.domoticz.com/wiki/PersistentUSBDevices
What I think, we need to understand how Home assistant or Hassio is creating those devices to create this file automatically.