Hi Ralph! Unfortunately, these features are GUI features and cannot be affected by the API. Closing a Ctrl-Z feature for a player cannot be affected by GM or Mod interaction either. Each player dismisses their own instance. Likewise with sharing a handout. If it's open on a player screen, it cannot be closed by external action, even if you delete the handout entirely. However... There is a new feature introduced this week that can hide posts in the chat. If you were to expose the graphic in the chat, you could hide it (manually, at this point in time) from all players instantly, by clicking the little three-dot menu button next to it.