Complex sentence: Arbitrators will place proposed items they believe should be part of the final decision on the/Proposed decision page, which only Arbitrators and clerks may edit, for voting, clarification as well as implementation purposes.
Split into simpler sentences: Arbitrators will place components they wish to propose be adopted into the final decision on the/Proposed decision page. Only Arbitrators and clerks may edit that page, for voting, clarification as well as implementation purposes.