Custom build step with Platforms package

The platforms package worked great for creating custom build configurations for different Storefronts (e.g. Steam, Oculus, etc.). The package changed quite a lot recently tough.

Previously it was easy to add a custom build step because it could just be added to a pipeline asset.

Now that the pipeline is not an asset anymore but just a class how can I add my custom build step?
It looks like the buildsteps are hardcoded into the pipline.

I just want to inject a custom generated version number for each build.
Is there a way to inject my build step or do I have to create a build pipeline from scratch just to use my custom build step?
I found the ClassicBuildPipelineCustomizer where I could set the version in
OnBeforeBuild but there is no way to reset this value after the build which leaves the project settings file in a changed state.

Besides that I am still confused about the naming of the Scriptable Build Piplene and the Platforms Package (see here): https://forum.unity.com/threads/scriptable-build-pipeline-and-platforms-package-confusion.975885/