LitCharts assigns a color and icon to each theme in Harry Potter and the Cursed Child, which you can use to track the themes throughout the work.
Parenthood
Time, Mistakes, and the Past
Friendship, Family, Love, and Bravery
Reputation and Expectation
Death and Sacrifice
Summary
Analysis
Back at the Potter house, Harry and Ginny start to argue about what Harry is doing to Albus, but they hear a knock on the door. Ginny leaves, and Draco enters, consumed by anger. He says that he has come to talk about Albus and Scorpius. Scorpius is devastated, and he wonders why Harry is threatening both teachers and Albus. Harry explains Bane’s prophecy and wonders if Scorpius might really be Voldemort’s son.
Harry’s fixation on the past, on Draco’s history and on his own shared with enmity with Draco from childhood, now drives Harry’s behavior. Draco has come to try to find a way to bring Albus and Scorpius back together, as he can see the way that Harry’s breaking of the friendship has caused his son pain. But Harry, focused on the past, can see no such thing.
Active
Themes
At this accusation, Draco takes out his wand. He and Harry start to duel, blasting spells at one another and dodging them in turn. Draco sends Harry twirling through the air, and Harry binds Draco tightly. Bodies and chairs fly as they hit each other with spells, until Ginny comes back in the room aghast and sets everything back in its place, asking what she missed.
The fact that Harry and Draco immediately take out their wands to duel illustrates how fixating on their histories as rivals has created deep problems in the present. As a result, Harry has made Albus and Scorpius miserable and is also causing conflict between himself, Draco, and Ginny.