I think I would re-express
await page.click('input[type=submit][value="Add Job"]');
as
await page.click(\"input[type=submit][value=\\\"Add Job\\\"]\");
i.e. replace the single quotes with double-quotes and escape them and then escape the escape for the inner quotes – i.e. the inner " becomes a \\\" – I’ve just noticed that the website’s parser parses my escapes, so mangling them. The code part is fine. It is supposed to be a triple \ before the double quote.
My heuristic on this is that there can be no single quotes in the json at all and then the curl command parameter can be surrounded by single quotes.