"Dear Imgui" is pure immediate mode both interface and implementation wise so far as I can tell.

Although it is worth noting that calls to Dear ImGUI don’t directly render, but rather build up state to batch render later with your graphics API of choice.

Fair.

"blitmediate"

The Windows API asks the application to redraw the window on certain events (e.g. resize).

The most popular immediate mode system I'm aware of is React, which definitely uses retained under the hood.

As a person who has used a slew of UI frameworks and written one or two: All of this is happening at a layer considerably lower than React.

This is what's happening when the browser redraws when you scroll for example. Arguably it has to do with the DOM, but certainly not how the DOM gets updated.

I think I'd argue that React is immediate mode with caching and then a retained-ish driver layer to talk to the underlying DOM.

But given the constraints of the "talking to the underlying DOM" part it's going to be a bit handwavey no matter how you argue it, I suspect.