Overlay

An overlay lives inside the app window, above its chrome. It is not an operating-system window and is not managed by the widget placement host.

Declare kind: "overlay" (or a list including it), include the exact overlay slot and register your component there. Position the component itself, for example using position: fixed. Keep pointer handling limited to the interactive content so it does not prevent use of the page underneath.

The supplied plugin-overlay has two insertions: a cockpit card and an overlay. It declares both kinds and both slots, registers both components and returns a disposer that releases both registrations.

Use this one-identity approach when the surfaces represent the same feature. Use a bundle only when the children need separate identities, configuration or toggles.