Today's build of Cantabile (3591) introduces "Detached" plugin editors, which is the ability for a plugin editor to go behind Cantabile's main window.
In previous builds, plugins always appeared on top of Cantabile's main window. While this helps prevent losing a plugin editor in the background, it does make it difficult to get back to the main window if you have plugins with large UI's open.
The new Detached option appears as a new command in the plugin editor menu:
When a plugin is detached, it's window works independently of the main window. For example the main window can appear in front of a detached plugin:
And detached plugins get their own representation in the Windows task bar:
By default, all plugin editors are attached but Cantabile does save the detached state of each plugin instance. Also it saves the state of the plugin GUI editor and the plugin parameter editor separately so you have have one editing mode attached and the other detached.