Paul Birch has described a number of high-concept space megastructures, including orbital rings, which could conceivably be adapted to become interplanetary elevators. They rely on streams of mass particles controlled by magnetic fields, which (he says) could have spacecraft riding piggyback on the mass-stream.
However a Hoffman transfer orbit is so much easier to use than any orbital ring system for transfers between planets that I can't see any immediate demand for an interplanetary elevator. Perhaps in ten thousand years...
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