supouse your human task are very similar: same input/output parameters, same assignments of input/output tasks variables and process variables (except for some task variables that act as constants values)...
From a "business process" is like copy and paste this first human task, but if I want to use it in other "business process" I have to create everything again.
Is there something that I can do to put that human task in the Object Library of the business process editor?
I would create that task as single task in a process and then refer to that process from other via reusable subprocess (call activity) and make use of process variables in the process and task definition so it can be fully reused. There is no support for so called global tasks as defined in bpmn2 spec so only way is to reuse processes.