Critics have accused Ms. Trump of using her position in the White House to promote her brand, whose hashtag, #womenwhowork, meshes with her carefully developed image as an advocate for women in the Oval Office. (Photos of Ms. Trump posing next to the Canadian prime minister, Justin Trudeau, or sitting in on meetings with business leaders have replaced pictures of her shoes and handbags in her Instagram feed.) Those criticisms are likely to intensify as Ms. Trump cements her official role in her father’s inner circle.

Mr. Kushner has sold some of his assets, including his stake in the Manhattan skyscraper 666 Fifth Avenue, to a family trust of which he is not a beneficiary, according to Ms. Gorelick. And she said Mr. Kushner does not have any involvement with the Kushner Companies, his family’s real estate development firm.

People close to Ms. Trump said her official title would not mean a discernible shift from the unofficial influence she has exercised with her father.

Hope Hicks, a White House spokeswoman, referred to Ms. Trump as “first daughter” and said her service as an unpaid employee “affords her increased opportunities to lead initiatives driving real policy benefits for the American public that would not have been available to her previously.”

During the presidential campaign, Ms. Trump was an advocate for a federal maternity leave policy as well as for affordable child care. Since her father’s election, she has coordinated a women’s economic council meeting that involved Mr. Trudeau, whom she later accompanied, along with his wife, to a Broadway play. And Ms. Trump will meet with Chancellor Angela Merkel of Germany, with whom her father held a tense Oval Office visit and news conference two weeks ago.

While Ms. Trump’s portfolio appears fairly circumscribed, Mr. Kushner has broadened his. He is Mr. Trump’s point man with some foreign governments and in working for Middle East peace, and he is at the helm of a new White House Office of American Innovation, which seeks to bring private sector concepts into the West Wing to streamline a bureaucracy whose upper echelons Mr. Trump has so far left largely vacant.