Example

Text { text: "&Username"; buddy: userNameInput }
TextField { id: userNameInput }

This is useful for two things:

1. Improve keyboard navigation. Alt+U will move focus to the item it is buddy for.
2. Accessibility can query the "logical name" of the TextField, providing more meaningful information to the a11y user.

Frameworks with similar concept

Qt

https://doc.qt.io/qt-6/qlabel.html#setBuddy

Windows.System.Forms API

https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.label.usemnemonic?view=windowsdesktop-8.0   (Label.UseMnemonic Property)

(Uses the tab focus order to find the next focusable item from the label)