That hose may actually feed into the heater control valve in between the 2 firewalls. It may actually be leaking from that valve or the small plate on top(about 2"x2") may need snugging down.

Sometimes when the monovalve insert is replaced the plate just mentioned is not snugged down enough and coolant will leak giving the impression that one of the hoses in the near vicinity is the culprit.

A cooling system pressure tester will definitely isolate it.