Get all registered plugin IDs.
Register plugin-contributed menu items (R2.3, C42). Items appear in a "Plugins" group in the menu. Call with the same pluginId to replace previous registration.
Resolve which menu items to show for the given target. Applies each item's filter function; items whose filter returns false are excluded.
Unregister a plugin's menu items.
Register built-in menu items (called once at init).