How can I save a clip to the bin for later use? (Clip defined as a portion of a video file set by in/out-points)
Extract zone creates a new video file and imports that into bin.

I assume you mean like Pancake Timeline Editing. Making pre-cuts and pull down what you need in the final timeline? If yes, you cannot do that as we have one timeline only. Workaround: make a video track on top. Put in all raw footage and make pre-cuts. You can put the same clip from the bin as many times as desired and make pre-cuts. Just hide/unhide this top track as needed.