President Obama has described Donald Trump as ignorant, dangerous and unfit to lead the nation, but he’ll ask the Republican president-elect Thursday not to wipe out his cherished, legacy-making executive actions on everything from the Iranian nuclear deal to Obamacare. In a meeting at the White House to prepare Mr. Trump for taking office, Mr. Obama will try to persuade the president-elect to honor what his aides call a “tradition” of preserving executive actions implemented by the departing chief executive. “There is a tradition, particularly with regard to executive agreements of successive presidents preserving some element of continuity,” said White...