Fortunately I discovered the extension for the German chart of accounts SKR03. I have used this extension with
sudo -H pip3.7 install triton-account-de-skr03 installed.
Besides, the command input didn’t help either:
sudo -H trytond-admin -c /etc/tryton.conf --update-modules-list
Unfortunately this module is NOT listed under the Modules tab. Did I ignore something? I am already grateful for the right hint.