How to use sdk correctly?

I wonder who uses the sdk?

  1. Developer
  2. flatpak build

I developed an application, should I write, test, run it in the sdk? Or in the host or virtual machine/container?

The specific ideas are as follows:
Develop in sdk, enter the org.gnome.Sdk//42 environment, but the process will always exist (ignore ctrl-d), and then the host uses a special shell, the operation of this shell is equivalent to running in the sdk shell, i.e. control org.gnome.Sdk//42 in the host

At this point, the development tools on the host (or on the flatpak) only need to allow shell encapsulation, as the encapsulation of all commands, to use org.gnome.Sdk//42 as a development environment.

Dependencies required for development (not present in the sdk) can be compiled and installed in the sdk. This can use a fixed prefix like /app. Doesn’t make sense in sdk/app, so it works.

--app-path cannot be used, the directory will become read-only. So need to soft link to /app

Does this make sense?