Composer plugins now have access to a closeDraft function, which both closes the composer plugin and the draft composer in Front. This is useful for plugins that send messages directly within the modal window.
For example, in the following screenshot, the Send Template button sends a message template through a channel, and uses the closeDraft function to close both the composer modal that contains the button AND the draft composer behind it.
Note that this method is available for composer plugins but not sidebar plugins.
Learn about the closeDraft function on the Developer Portal.