Works 🙂 Many thanks!
My workaround: delete the content of the local.yaml.
Solved with the latest app package release today
i managed to make the changes, i had two mistakes:
i had to clear the kimai cache via terminal (it is in the kimai docs)
when trying to clear, so the effects take place, i got an error. apparently you cannot use tabs as indentation, so my local.yaml was not readable anyway
after using spaces and clearing successfully the cache, every worked 🙂
thanks for the help!