The IPC has published the Tokyo 2020 Paralympic Games Qualification Guidelines with the details of how Para badminton players qualify for the Tokyo 2020 Paralympic Games.
You can download the full version of the guidelines published on the IPC website (linked here).
The principles applied by the IPC to ALL sports are detailed on pages 3 – 13.
The Badminton section starts on page 36 onward. The qualification system for badminton is complex so we recommend to read all the detail to understand the process.