Just use the cables from the amp as intended & tape off the extra terminations at the speaker end, to avoid causing a short. You can either use a jumper or another set of cables from the amp.
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There is no problem doing what you want to do other than if the cables have some type of network box or "directionality" to them. I would not suggest leaving any cables that are connected to the amp unattached at the speaker end. This could open up the door for the cable to act as an antenna for RFI along with playing games with impedances that the amplifier sees. Sean
I'd like to add more. If you use both amp outputs there's a possibility that there will be a problem, such as a resistive load when both sets of terminals are used which may or may not cause a problem with the amp & again may or may not cause a degradation to the sound quality. Depends on if the outputs will be bridged, on the load impedance, running in parallel & whatever else goes on when you do this.
You could also stack the bi-wire ends at the speaker if there's room & still use a jumper. It depends on the terminations of all involved.
If you have bi-wire cables and non-biwire speakers, just put both + wires together (and minus) on the single speaker terminal. Then run a jumper.
Your speakers were probably designed for two separate pairs of speaker cables, instead of an internal biwire pair.
The two sets of outputs on the amp are probably wired together inside the amp. There is no benefit connecting all 4 separately.