> So I’ll certainly reuse your tests, but will have to redo the implementation.

That's fine, but please bear in mind what I said about a 100% declarative approach being insufficient - see the Windows example I gave, where Windows APIs have to be called at installation time to determine how the categories are set up. My tests don't cater for that, but in my view it's an important requirement that shouldn't be lost. That's why I put the code into a hook, install_data being the one which required minimal changes to the code.

I'm not wedded to the specific implementation, simple though it is - I was aiming for a solution that worked and would be easy to review. I agree that install_data may not be the best section for this, and the global section seems more reasonable. But the key thing, apart from the parsing logic etc., is to allow changes / additions to the categories to be made at installation time by user-defined code (=> hook).