Yes, I agree. I don't see much practical use in this. I was just surprised how (relatively) straightforwards this is to do, and thought it was more cool than useful
Often I also find the opposite problem ... sure, you can do some stuff in (c++) metaprogramming, but can you (at compile time) generate a JSON/XML/YAML file that can be fed to some other part of the system?
The opposite 'toString' problem seems harder - I didn't try, but it should be possible now that std::string is constexpr.
I don't think you could parse it with, say, a class that has a std::string member (because of the transience restriction), but perhaps you can use lambdas that capture that string by reference, and call each other as appropriate?
As for exporting that as some sort of compiler artefact for use elsewhere, I am not sure how you would do that...