I usually need to restore Dolphin's instances at startup in their same folders when the system turned off. Specific applications, listed in some textbox, should be specified to be restored just like "Applications to be excluded from sessions" in System Settings/Startup and Shutdown/Desktop Session.
This needs to be implemented on a per-app-basis I'm afraid. Marking as a duplicate of the bug tracking this for Dolphin. *** This bug has been marked as a duplicate of bug 413564 ***