Can anyone tell me how to change how task priority levels are set (=tp!priority)

Task priority is an option that can be set in the general tab of the node properties. A task priority is generally configured to change to indicate escalations. When configuring escalation for a node, one of the available escalation action is to modify the task priority. The default priority for all tasks is "normal". There is also a Task Smart Services Plug-in that allows you to set priorities for tasks (available under shared components)