Can I save display data daily at 12am with SMARTDAC+ GX/GP series?

Yes. Set the length to something longer than 1 day, and set a match time timer of 0 hr 00 mm. Next, make the match time timer an event, and set saving of display data as an action. For setting examples, see section 1.19, "Configuring the Event Action Function" in the user's manual.
User's Manual (IM 04L51B01-01EN)