@zygoloid , did you have something like this in mind?

Alternately, we could eliminate the table and make the definitions explicit in the synopsis:

#define __cpp_lib_concepts 201806L // Also in: <concepts>

It seems silly to have a synopsis with simply // what the table says, and equally silly to have a table to depict things that we could as easily declare directly.

I like @CaseyCarter's suggestion. Let's try treating these like any other macro the library provides.

Here's how a proper synopsis with #define would look like:

If desired, I can add section cross-references after each mention of a header. Please advise.

IMO the cross-references would look cluttered (especially if given on every mention of a header, not just the first mention).

I like this. Has anyone already done a pass over a before and after document to check that the macros and versions all match? This seems like an easy change for a typo to slip into unnoticed.

Has anyone already done a pass over a before and after document to check that the macros and versions all match?

I have just performed such a pass; it's all good.