As I wrote in my first post I am absolutely new to unraid. Today I found a tutorial how to build your own templates for docker hub containers via "Add Container". This is much easier than I thought. That was the crucial information I was missing 😉, now I could install the Firefly III Data Importer (FIDI) myself without any problems. Thanks for the support with the screenshot. And if I had known before how easy it is, I would not have asked... 🤓