[AllanJ]

No harm is done disabling the secondary heating (heat strips) in a heat pump system to cut down on expensive resistance heating utilization.. The easiest way to disable the strips is to flip off their breaker The only problem is the house being cold because the heat pump by itself doesn't deliver enough heat. The latter problem is being combatted with a tertiary system, here, a wood stove although it could alternatively be a stand alone perhaps preexisting gas or oil heating system.

Now that we have established that the strip heating is not necessary (on the OP's project) he is free to commandeer a cable and breaker that feeds only strip heaters and use that for somehing else of his choosing (and also code compliant regarding a white neutral conductor, etc.). It would also be nice to label the protruding orphaned (and unenergized) ends of the wires for the strip heaters so the next owner of the house not wishing to manage a wood stove can reconnect the strips.

I would second running new wiring even if in conduit or Wiremold exposed on the wall as superior to modifying the circuitry within the heat pump unit to free up a cable from the panel for some other purpose. I do not like the idea of being a new homeowner moving in and finding, only after considerable perusing and matching up of actual wiring and the schematic, that an appliance or equipment that looked perfeclly normal on the outside had been bastardized inside.

Did I miss something (by failing to parrot the second sentence of reply 11, by the OP)?