This is the best there is at the moment.

https://ninoxdb.de/en/manual/calculations/reference-of-functions-and-language

If you are new to programming, you might want to look at some Javascript tutorials to give you the fundamentals. Fabio said Ninox is based on Javascript.

https://ninoxdb.de/en/forum/technical-help-5ab8fe445fe2b42b7dd39ee7/set-date-field-with-a-choice-field-is-made-5c13dbeb59e23c381bb96f5f?post=5c176fa459e23c381bb96fcb&page=1

I’d really like a proper manual for coding with syntax, functions and objects.

Check www.nioxus.com for a good manual and tutorials and even videolessons.

Seems like the link is broken, here is another one: www.ninoxus.com