@whynothugo Yeah. Cosmic-panel, like cosmic-comp, uses the Smithay library to implement a compositor. It would be nice if Smithay or a library on top of it made it easy to write a nested compositor for uses like this, but currently it's a bit complicated.

Qt also includes a compositor: https://doc.qt.io/qt-6/qtwaylandcompositor-index.html. A nested Wayland compositor seems to be the modern alternative to XEmbed/etc., but there could be more libraries to make it easy.