@BrutalBirdie Thank's for your answer.
I'm not so familiar with Cloudron installation.
I have read the linked documentation.
'If you require a custom module that is not installed in /app/code/node_modules, please make a post in our forum.'
I would like to have following custom module installed in /app/code/node_modules:
n8n-nodes-ninox
And how i have to write the added line like for /app/data/env:
export NODE_FUNCTION_ALLOW_EXTERNAL=???