Question First Time in Europe: Ljubljana and Croatia Itinerary Help

This is our first trip to Europe, and we're super excited but also a bit overwhelmed with planning. We have about 10 days in June and are thinking of visiting Ljubljana and Croatia. We're looking for advice on must-see spots, hidden gems, and any travel tips for first-timers in these areas. How should we split our time between Ljubljana and Croatia? Are there any specific places in Croatia that are a must-visit? Also, any advice on transportation between these destinations would be greatly appreciated. Looking forward to your suggestions!