You are PM and you have team member was negative then change to support at midway, which document you will updates SH management plan or HR management plan? Saving Changes...
I would not usually capture team member attitude or engagement in either of those plans as I usually would develop and share those with the team. I'd say this is one change that a PM should gratefully recognize but NOT formally document...
I believe that team member is SH so Project managers should be aware of the sensitive nature of the stakeholder management plan and take appropriate precautions.