(How) Can I pre-install a CLion backend in the image used for my dev container?

Hello, simon.beyer.external.

Unfortunately, even if you add the IDE backend installation to the image build steps, the deployment process will run regardless, and it doesn't support using a pre-installed IDE backend. With the devcontainers.use.separate.project.panel registry key enabled you may either specify the local path to the backend archive or a URL to get this archive from.

Whenever there is a new image, the IDE must be downloaded from scratch into the dev container on my developer machine, and this takes a lot of time.

The IDE backend is not downloaded from scratch unless the new version is used; the already downloaded backend versions are located inside the jb_devcontainers_shared_volume Docker volume and are used directly from there.

Here is shown that I can tell the dev container to start the IDE backend… but it is unclear to me, how that helps:
The IDE backend is started just fine without that setting. I have been using it for months.

The customization option mentioned by this link just specifies the type of IDE backend used (CLion, IntelliJ IDEA, PyCharm, etc.) and is relevant for the automatic backend installation only (when the Choose the backend version automatically option is enabled in Settings | Advanced Settings).