The node classification screen in admin studio allows you to associate an agent with a node type, e.g., 'Backgroundprocessing'. which is a class of Background nodes. If needed, you can define your own custom node type for a particular use case. For example, define your custom node type (using -DApplicableNodesTypes to specify the list of node types you want).

You also can define the node on which agent to be run. For ex, we want Agent A1 to run on Node N1, then create a decision table and under conditions, check for A1 AND N1 and return True otherwise return False. This can be configured in Agent activity.

If you want to stop agent run temporarily on a node, then you can do it from Admin Studio - Agents landing page. This is effective until the next restart of the environment.

https://community.pega.com/sites/default/files/help_v84/pxadminstudio/procomhelpmain.htm#engine/agents/eng-agent-management-con.htm

If you want to restrict permanently, then consider assigning a custom node type for that particular node. From Pega 8, now the schedules are created per Node Type.

https://community.pega.com/sites/default/files/help_v84/procomhelpmain.htm#engine/node-classification/eng-configuring-node-types-for-agents-and-listeners-tsk.htm