Menuconfig
To edit the application Kconfig using menuconfig (a text-based interface that runs in the terminal), go to the "Applications" view, right-click on the application > Configure > Menuconfig. With several build configurations, the tool edits the active one: use Set Active on the target configuration first (see Multibuild).

The command runs west build -t menuconfig in the application's terminal.
tip
Prefer a graphical editor integrated in VS Code? Use the Kconfig Manager, first entry of the same "Configure" submenu.