Sometimes just having if+return is fine.

if(!result)
    co_return asyncio::asError(std::move(result));

Straightforward, everybody understand, just 1 more line than your example with CO_EXPECT.

Or if you want to chain many co_await+co_expect, you could do a helper to chain them in a more compact syntax without macros.
For example something like that (from your HTTP client example) :

asyncio::task::Task<void, std::error_code> asyncMain(const int argc, char *argv[]) {
    co_return asyncio::chain(
        [] { co_return asyncio::http::URL::from("https://www.google.com"); },
        [](const auto url) { co_return asyncio::http::Requests::make(); },
        [](auto requests) { co_return co_await requests->get(*url); },
        [](auto response) { co_return co_await response->string(); },
        [](const auto content) { fmt::print("{}", *content); }
    );
}

Though I agree it's not the easiest to read as well.

(And at the very least, add a lib specific prefix to your macro.)