It DOES appear that you can edit a scene after you create an automation to include a mode change on both sides of an If . . . Then clause.
Of course, this means in order to change modes you must create 3 scenes for each mode:
Scene w/o mode change (e.g. to set lights without a mode change).
Scene with mode change for use in an automation.
Scene with mode change only.
This is insane! Note, also, finding the current mode is very difficult to find. The only place I can find it is under Manage Location.
Can the Smartthings development group please go back to the drawing board on this?