Where is defined "$L.can.retract" variable?

I'm making changes to Change management and would like to get "Retract" option to Approval phase, now there is only "Approve" or "Deny". Where is defined that the operator can Retract an approval?

 

After this I'm planning to make changes to the process so that after "Retract", change is automatically send back to Planning phase so that Coordinator can make needed updates to the Change record before next approval round. What do you think about this kind of process?