One very commonly used features in OpenNMS is categorize the nodes to simplify the configuration common to certain groups of nodes.

Having this in mind, it would be very useful to be able to list all the nodes for a given category, for the same reason we have a drop-down list on the "Node List" page to filter the nodes per Location.

Using Categories is more common than using Minions/Locations, so having the same functionality will help a lot.

As a plus, updating the search page to be able to find nodes per category will also be extremely beneficial, specially on those cases where OpenNMS is managing thousands of nodes and the "Node List" page takes a while to render.