The Constitution says this:
[The President] shall nominate, and by and with the Advice and Consent of the Senate, shall appoint [...] all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law [...]So, the President may appoint Officers of the United States not specifically mentioned in the Constitution. The requirements seem to be that these positions be established by law (i.e., legislated into existence by Congress) and appointed only with Advice and Consent of the Senate.
This would seem to imply that any Presidential appointment not specified by the Constitution needs supporting legislation, and since Senate confirmation seems to be the accepted interpretation of 'Advice and Consent,' well, there you go...
Except the next line is this:
[...] but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone [...]So, it seems we need to know if there is a law, passed by Congress, that allows the President such wide discretion in appointing such 'czars'. I honestly don't know whether such a law is on the books.