May I ask if there is a complete source code project for this instructional video that needs to be learned.
Work with Reality Composer Pro content in Xcode
Work with Reality Composer Pro content in Xcode
The companion sample for that session is Diorama.
This is the same project demonstrated throughout "Work with Reality Composer Pro content in Xcode" (WWDC 2023 session 10273) and its companion sessions "Meet Reality Composer Pro" (10083) and "Explore materials in Reality Composer Pro" (10202). Opening the Diorama project in Xcode and working through the steps in the video should closely match what you see onscreen.
Note that the session is from WWDC 2023. Reality Composer Pro and its Xcode integration have continued to evolve since then, so if you're learning this for a current project, I'd also recommend watching "Compose interactive 3D content in Reality Composer Pro" (WWDC 2024 session 10102), which covers newer capabilities introduced after the 2023 sessions.