wger support - garawaa/openScale GitHub Wiki
To gain your wger REST API Key log into https://wger.de and go to About this software -> Rest API
then on the right side you see a button Generate API Key
click on it and copy your API Key into openScale sync.
Note: Wger only supports one measurement a day. If you have more weight measurements in openScale a day, only the first one are synchronized to wger.