Plugins currently have no official way to store volatile per-machine data (window positions, dialog geometry, last-used directory paths, dismissed warning flags, UI state).

Today a plugin must either:
  
 - Use plugin_config — but this participates in profiles and gets synced, which is overkill for transient UI state
 - Reach into global_config.persist — undocumented, pollutes the global persist namespace, no isolation between plugins

Proposal:
  
Add api.plugin_persist to the plugin v3 API — a plain ConfigSection (no profile participation) namespaced under [plugin_persist.<uuid>],  with the same register_option() / [] access pattern as plugin_config:
  

  def enable(api):
      api.plugin_persist.register_option('last_directory', '')
      api.plugin_persist.register_option('dialog_dismissed', False)
  
      api.plugin_persist['last_directory'] = '/home/user/music'
      last_dir = api.plugin_persist['last_directory']

This gives plugins a clean separation:
  

• plugin_config: user-configurable settings (profile-aware, synced)
• plugin_persist: volatile per-machine state (no profiles, disposable)
    
  Data in plugin_persist may be cleared during major version upgrades (same semantics as core persist).