Show me in the Constitution where a subordinate in the executive branch has the power to indict his superior. Who does that subordinate answer to, if not the chief executive.
It’s absurd to interpret the Constitution as creating a class of nobility that’s above the law.
You're setting up a straw man fallacy. Nobody is saying that the president is above the law. The president can be impeached, removed and then indicted.
Cite the article, section and clause that prohibits it. There is one for members of Congress, but not one for the President.
There's nothing in the Constitution that even suggests a subordinate can't arrest and indict a "superior." If there were, the UCMJ would be Unconstitutional: It allows for exactly that. Look it up.
If Mueller can indict the Attorney General, he can indict the President. The same is true of any other Federal prosecutor. Federal prosecutors are Constitutional officers: They must be confirmed by the Senate:
[The President] shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.
Note that not all Constitutional officers need be appointed by the President. Some can be appointed by other officials, even judges.
Such officials swear to uphold the Constitution; they do not swear to obey the President nor serve him instead of serving the country.