How can I Make Custom Launcher with 2D multitasking

I want to develop a system launcher to replace Oculus's launcher through Unity 3d or Others, including calling other 3D and 2d apps, and supporting 2d multitasking, but I haven't found an api that can replace the launcher and call 2d multitasking. At present, I can call other 3d apps in 3d apps and return, but when calling 2d apps, the system launcher window will open directly, and 3d apps will be suspended,I hope to be able to operate native 2D apps with 2D multitasking like launchers in VR applications,Are there any relevant APIs, source code, or sample projects that can help me with document links or keywords in the future