Due to the way that Cubase handles open plugin GUIs, getting inserted plugins to follow the track selection of a UF1/UF8/UC1 is not possible.
In Cubase, by default, the 'Return' key on your keyboard will open/close your 'editor' window. The workaround for this would be creating a macro to trigger either the 'Return' key, or, your own customised Cubase Key Command for opening/closing the editor. This can be assigned to any of the user assignable buttons on your UF1.