It has become a tradition that on the night of the State of the Union speech, some noteworthy personage sits with First Lady Nancy Reagan in the balcony of the House of Representatives. Last year it was Jean Nguyen, the Vietnamese refugee who graduated in June from West Point. On an earlier occasion it was Lenny Skutnik, the man who dove into the Potomac to rescue survivors of the 1982 Air Florida crash on the 14th Street Bridge.

About five weeks ago, according to knowledgable sources, two members of the White House staff had the idea that this year's guest in Nancy Reagan's box should be Jonas Savimbi, leader of the National Union for the Total Liberation of Angola (UNITA), a rebel group fighting the Marxist central government. Savimbi arrives in Washington today for a much-ballyhooed visit in which he is looking for moral and financial support for UNITA.

When the idea was discussed, though, officials quickly encountered "a thousand reasons why you shouldn't do it," as one source put it. Principal among them was the fear that a large number of members of Congress might walk out of the chamber or boo if the president introduced Savimbi as his hero of the year. Many in Congress have the impression that Savimbi is a stooge of the South African government, not the freedom fighter his allies here depict.

"It's one thing to have Sister Mary Mercurochrome or some Boy Scout who saved a bunch of people," reflected a source familiar with the White House debate about whether or not to canonize Savimbi. "But it's a different kettle of fish to have some guy who's been in the jungle fighting the godless commies sitting next to Nancy Reagan."

More on Marcos . . . The controversy over Philippines President Ferdinand A. Marcos' World War II service is causing problems at the State Department. Officials trying to keep the record straight about what Marcos did or didn't do during the Japanese occupation of his country are having trouble keeping up.

A major stir was caused here last week by news reports revealing the existence of wartime documents challenging Marcos' claims to have been a leader of guerrilla resistance against Japan, and suggesting that he actually spent much of the war working on behalf of Filipino politicians who collaborated with the Japanese occupation of the islands. In some U.S. Army reports, Marcos' assertions about his war record were described as fraudulent; the United States rejected his bid for post-facto recognition of his alleged role as an anti-Japanese guerrilla leader.

Senior State Department and Pentagon officials, asked about the situation by the Senate Foreign Relations Committee, diplomatically replied that they didn't have enough information to answer such a sensitive question on the eve of the Feb. 7 presidential elections in which Marcos is seeking reelection.

But the State Department's bureau of public affairs yesterday released a 20-page fact booklet for people seeking information on the upcoming election. Its biography of Marcos began: "A war hero, lawyer, and experienced legislator . . . ," then added: He survived . . . Japanese torture, eventually escaping to lead resistance guerrilla forces . . . . "

Farmer Bush? . . . There's increasing talk that Vice President Bush's minions, with an eye obviously on a 1988 campaign, are discovering the agricultural crisis. Bush aides are reported to have taken a more than passing interest in the selection of a successor to recently resigned Agriculture Secretary John Block; the VP himself is said to have spent time recently with an Iowa farmer friend, getting a fix on the political picture in the Corn Belt and talking farm problems.

Who's In Control Here? . . . It's time for a major reorganization of the National Security Council, according to officials elsewhere in the government. Following the Dec. 27 airport terrorism at Rome and Vienna, at least six different members of the NSC staff informed the State Department that he or she was coordinating the policy making that led to economic sanctions against Libya.

Turnage to Head VA . . . President Reagan said yesterday he will nominate Thomas K. Turnage to head the Veterans Administration.

Turnage, who will succeed Harry N. Walters, has been director of the Selective Service System since 1981. He is a 40-year veteran of the Army and National Guard, and attained the rank of major general.

The White House also announced that Andrew John Strenio Jr. has been nominated to succeed George W. Douglas as a member of the Federal Trade Commission. Strenio is an attorney and was a member of the Interstate Commerce Commission from September 1984 until last Dec. 31. From 1982 to 1984, he was assistant director for regulatory evaluation in the FTC's Bureau of Consumer Protection.

The nominations must be confirmed by the Senate.

New Pentagon Lobbyist . . . At the Pentagon one hears that Margo Carlisle, former executive director of the Senate's Republican Conference, is to be named assistant defense secretary for legislative affairs. As the Defense Department's chief lobbyist on Capitol Hill, Carlisle would be the highest-ranking woman at the Pentagon