Service Desk plugin has a number of screens but those screens does not have a context. As a result, other plugins cannot attach anything to those views like the portal page (servicedesk/customer/portal/XYZ).
So, it will be useful to introduce a new web resource context for a portal page.

If your plugin adds a number of screens to the application, you may find it useful to introduce a new web resource context for your plugin that your plugin web resources (or any other plugin web resource) can hook into, to be automatically included on these screens.
To introduce a new context in your plugin Velocity templates, you can call the requireResourcesForContext() method on the WebResourceManager object from your Velocity templates:

$webResourceManager.requireResourcesForContext("com.acme.plugin.fancy-context")

This will include any resource in the page that specifies a context like this in its definition: <context>com.acme.plugin.fancy-context</context>.