Is there an option to keep only one instance of DOpus open at a time? (Or maybe I should say "one lister window" at a time?) I looked around Preferences but can't seem to find an option. If I switch to another layout I would just like it to replace the current one, not open a new window.
For layouts, turn on Preferences / Layout / Saved Layouts: Close existing Listers when loading a new layout.
You can also make buttons which load layouts and do or don't close existing listers regardless of the preferences setting, if you need to override it in some cases but not others.