Field Overwrite within process no option to keep seperate .

So i have the workflow setup to enable some leave request approvals.

I have faced this problem where the comments field if returned to the initiator or the process for editing is being overwritten and not kept as separate value so that i could show in my Grid or Data lists as a separate entry , instead it just gives the user an edit box of the previous value with the option to edit/overwrite  that. I understand that all changes and actions are kept in the Audit log if i enable the Audit plugin but how can i make a field not get overwritten each time it is being used for input ?