With password on both databases it’s possible for DC app to select and open the one without showing any selection dialog. There will be only password entry box on the launch. Even no hints in settings needed. To open another database, you just need to kill the app.
BTW one of most technically advanced Telegram forks was crtated by people from Bilarus. Guerrilla Telegram, or something like that. It allows in some critical situation (which for them seems to be very real and maybe even usual) to hide some ‘wrong’ chats, show some ‘very good’ chats, and silently send messages to frends with special panic message and geolocation. (I didn’t try it myself.)