OR, you can open any of the files under the android subdirectory for
editing. You should then see a “Flutter commands” banner at the top of the
editor with a link  labeled Open for Editing in Android Studio.
Click that link.

For both options, Android Studio gives you the option to use separate windows or
to replace the existing window with the new project when opening a second
project. Either option is fine.

If you don’t already have the Flutter project opened in Android studio,
you can open the Android files as their own project from the start:

Click Open an existing Android Studio Project on the Welcome
splash screen, or File > Open if Android Studio is already open.

Open the android subdirectory immediately under the flutter app root.
For example if the project is called flutter_app,
open flutter_app/android.