I know I could just list the values, but then I need to know in what order they shall appear - and that is exactly what I want to avoid.
There are no shortcuts. You do need to supply the data in the correct order, or write your own code to initialize the members.
Should I conclude there is no way to init a struct using its field names?
The field names must be used when you want to initialize one field at a time, in your code. They are not to be used when you want the compiler to do the initialization for you.