Are there any plans to write a nice abstraction layer so that the user is not forced to use swing but can implement what he wants to use himself?

These plans exist, but no ETA. Ideally we want to provide Swing-independent entry point for Compose. There is also another entry point -

TestComposeWindow

that doesn't use Swing under the hood, but it is only for rendering Compose into bitmap, and currently isn't very flexible.

This would be awesome to have to put Compose inside any JVM game for example, to build uis. Is kinda annoying the requirement to rewrite all the compose desktop classes just for put Compose in another OpenGL Context for example.