Resources, with an icon and current amount, are always displayed at the top of the screen. This is, of course, very useful for most resources, but if we were to use, say a "hero" resource, to ensure the player can only have one of a specific kind of unit (out of multiple choices; for example, you have three choices for hero units, but can only have one at a time, so we'd want to use a static resource that is recuperated upon the death of that unit).
Using a resource is the easiest way to do that, however, we don't really need it to be shown in the top HUD. The best approach would be to simply hide that resource in the HUD, toggled via an option XML tag,
<display value="true|false"/>. If true, the resource is displayed as normal, if false, the resource is hidden from the top HUD. If the tag is omitted, the default is true.
The tag in question already exists in GAE as the above code, and is further documented
here.