There are several ways to open the Hyper Editor in Logic Pro.
Click the Hyper Editor button at the bottom of the Arrange window (or use the Toggle Hyper Editor key command, default assignment: Y).
Choose Window > Hyper Editor (or use the Open Hyper Editor key command, default assignment: Command-5).
Drag the Hyper Editor button, which changes to the Hyper Editor window as you drag it.