Blatant exploitation of West German Chancellor Helmut Schmidt's "courtesy visit" to Ronald Reagan here, carefully plotted to circumvent the president-elect's aides, has diminished chances for a restoration of U.S.-West German harmony following corrosive relations the past four years. u

The crafty Schmidt breached Reagan's announced policy of meeting no foreign leaders until after Jan. 20, then returned to Bonn to brag about it before the Bundestag. Schmidt bypassed regular channels to see Reagan, using personal American friends. The most important: industrialist (and possibility for secretary of state) George Schultz, whose help was sought by West German Ambassador Peter Hermes. That exposed worrisome shortcomings in the Reagan operation two months before Inaguration Day.

The president-elect's closed-door policy had barred a Reagan meeting with Israeli Prime Minister Menachem Begin. But the policy fell apart when Reagan transition chief William Casey accepted Shultz's recommendation that old-friend Schmidt, long regarded as the European pillar of the Western defense system, be admitted to Reagan's presence for a "courtesy" visit.

Reagan was pressed by Casey, who still hankers to be secretary of state. He agreed to say hello to Schmidt. Careful strictures were laid down by Reagan's aides: a " courtesy" visit lasting a few minutes, during which Reagan would neither be asked nor say anything important. Schmidt stretched it to a full 50 minutes. Every minute the meeting lasted, the more important it would look to the world.

Returned to Bonn, Schmidt stunned the Reagan camp with his bundestag speech. His description of "talks" and "dialogue" with Reagan ignored major Reagan-Schmidt differences about detente. He made it seem that Reagan was in full agreement with him on relations with Moscow, but in fact Reagan said absolutely nothing beyond the amenities.

"The president-elect announced he would be seeing no foreign leaders," the ambassador of one NATO member told us. "Well, he surely was to be believed, but then came Schmidt and now we do not know." So did Schmidt undercut Reagan's early credibility within the alliance.

Involved here is not just the problem of Schmidt's indiscreet conversion of Reagan's "courtesy" gesture into what he grandly told the Bundestag was a "dialogue" on major issues. Also at stake is whether Reagan's operation can insulate him from end-runs, such as Schmidt's, around his regular staff advisers.

An end-run was made before the election when Reagan agreed, outside normal staff channels, to back A. W. (Tom) Clausen, Bank of America president, as the new president of the World Bank. The swift-footed Shultz also played a role in that circumvention of Reagan's staffers.

The case of Chancellor Schmidt will prove more troubling. Breezing into Washington for what had originally been planned as a summit meeting with presumed election-winner Jimmy Carter, Schmidt found himself crossed up by the American electorate.

The day after the election, Schmidt's agents here began proselytizing Reagan's intimates, outside regular channels. They wanted a meeting that would enshrine Schmidt above all other U.S. allies and appear to dillute significant differences between Reagan and Schmidt on how to deal with Moscow.

Wounded feelings apart, Reagan's concession to Schmidt transmitted a false signal to Bonn and the world. The correct signal -- one that sooner or later will be avoidable -- is that NATO is heading into the roughest waters of its existence. Reagan's advisers intend to bear down far harder than Carter did on Schmidt for breaking his commitment to a 3 percent real increase for defense.

A deeper Reagan-Schmidt problem lies in their philosophical gap over detente with the Soviet bloc. Schmidt's failure even to mention that gap, though it may prove much wider than differences during strained Schmidt-Carter relationship, was viewed by some Reagan aides as disingenuous.

Reagan himself has kept silent about being sandbagged by [WORD ILLEGIBLE] silence is not consent. [WORD ILLEGIBLE] coup in presenting [WORD ILLEGIBLE] new best friend makes the [WORD ILLEGIBLE] between Washington and Bonn even more difficult.