[A11Y] Fix keyboard navigation for adding a new launcher

[andre-code]

Description

The navigation from the "Add New Launcher" modal to the "Existing Environment" or "Custom Environment" form modals is not functioning correctly. The focus should automatically shift to the newly opened modal. Additionally, when selecting "Existing Environment," it is difficult to smoothly navigate and select the environment using the keyboard.

Steps to Reproduce

Create a custom session launcher using only the keyboard.
Create an existing environment launcher using only the keyboard.