SEOUL—When Kim Jong Un stepped off his bulletproof train in Beijing for this week’s extravagant commemoration of China’s victory in World War II, a smiling woman dressed in a demure navy pantsuit stood close behind the North Korean leader as he greeted China’s foreign minister.

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In recent years, she has accompanied her father to missile and satellite launches—high-profile events that Kim has used to showcase North Korea’s status as a nuclear power.

To be sure, Kim’s daughter appeared to otherwise play a minor role in Beijing, remaining largely unseen apart from her arrival Wednesday.

But her presence—in what may have been her first overseas trip—sent a clear signal, analysts say. “The Kim regime is normalizing the idea of her being the successor, or at least a very powerful presence in North Korea’s political system,” said Peter Ward, a North Korea researcher at the Sejong Institute think tank in Seoul. “She also helps humanize Kim’s image.”

While Kim may be grooming his daughter, she is too young to formally be designated as successor, say analysts. Moreover, Kim is only 41. His father, Kim Jong Il died at 69, while his grandfather died at 82. Kim’s grandfather founded North Korea and his son took over as leader on his death in 1994.

It is unprecedented for a woman to take power in a dynasty dominated by men, although female members of the Kim family—including Kim Jong Un’s sister—have wielded considerable influence.

Traditionally, North Korea hasn’t revealed much about the Kim family members’ childhood. That allows the regime to carefully control the propaganda surrounding how they grew up.

Kim himself was largely hidden from the public view as a child. It only became known that he was selected as successor around three years before he assumed office. Kim was in his late 20s when he took power in 2011 after the death of his father.

North Korea hasn’t publicly revealed the name or age of Kim’s daughter, referring to her as the “beloved child.”

In 2013, former NBA star Dennis Rodman said he had met Kim’s daughter, claiming she was called Ju Ae. A former South Korean spy agency officer and former North Korean diplomat have said she has a different name. South Korea’s spy agency has said the girl, likely Kim’s second child and born in 2013, appears to be the most likely successor for now.

Since her first public appearance at an intercontinental ballistic missile launch in 2022, Kim’s daughter has accompanied her father to military events, including a satellite launch and military parades, as well as diplomatic events such as a visit to the Russian embassy in North Korea in May.

In Beijing, Kim chose to bring his daughter to an event that was of particular international importance for Pyongyang. Kim was a guest of honor of Chinese leader Xi Jinping, who used this week’s lavish celebrations to flaunt Beijing’s leadership of an alliance that is challenging the U.S. and its allies. Kim and Russian President Vladimir Putin flanked Xi at a massive military parade in Tiananmen Square. The Iranian president stood nearby.

By standing alongside two nuclear powers, Russia and China, Kim projected an image of a politically significant leader with nuclear ambitions, said Park Won-gon, a professor of North Korean studies at Ewha Womans University in Seoul. Kim regards nuclear weapons as indispensable to continuing his family’s rule of the country and to deterring aggression by foreign states.

“The only reason he could stand front and center [in Beijing] is because he too, has nukes,” Park said.

Kim’s daughter wasn’t the only offspring to appear at China’s celebrations commemorating victory over Japan in World War II. Belarusian President Alexander Lukashenko’s son was also spotted at a reception in Beijing on Wednesday. The son had previously attended China’s 2015 Victory Day celebrations when he was 11 years old.

Write to Dasl Yoon at dasl.yoon@wsj.com