Croatia Itinerary

Have you mapped out all of the drives?
You don't give any details about what you will be doing, so what kind of feedback are you looking for to help? You could possible consolidate some to limit moves (I would not go all the way to Sarajevo for one night for example), but not knowing your reasoning it is hard to advise.

Overall, the itinerary is far too rushed and is trying to cover too many countries, I think. Driving from Dubrovnik to Kotor can be replaced by a three-hour ferry ride. The border crossing formalities from Croatia into Montenegro by land can be time-consuming and involve waiting in a lengthy queue. You’ll be doing that twice in two days.

It would be more helpful if you list the nights. For example, Drive to Split and Hvar. Hvar is a ferry ride from Split. Are you going for the day or overnight?
Are you doing a day trip to Kotor or staying overnight?
You don’t want a car in Dubrovnik, very expensive to park and difficult driving - narrow roads, many one way so you are driving in circles to get around. You can bus or ferry to Split then rent a car and drive to Slovenia, then Zagreb and drop the car.
With such a short trip I would drop Sarajevo.

Driving from Dubrovnik to Kotor can be replaced by a two-hour ferry
ride.

That’s what I call a high-speed ferry. Well done. But I think it takes 3 hours. But I could be wrong. https://adriatic-lines.com/dubrovnik-montenegro-ferry?gad_source=1&gclid=Cj0KCQiAwtu9BhC8ARIsAI9JHakWNrry6KpS8StNFrYulF9zc3vu5ggdWy5eFnU2gHFqh7aWIY7wYM4aAql7EALw_wcB

I suspect that on the boat upon arrival there will be a passport check, maybe one before departure as well. Be interesting to see if they do it like on a bus. Where the collect all the passenger passports at once then go through them one at a time for 30 minutes? Gotta do it leaving Croatia and gotta do it arriving in Montenegro. Count on time for that. Might be a half hour or more. Don’t know.

The border crossing formalities from Croatia into Montenegro by land
can be time-consuming and involve waiting in a lengthy queue. You’ll
be doing that twice in two days.

The drive takes 2 hours plus the border crossing. Of the three times I have done it the longest wait was about 30 minutes. But 3 crossings in 8 years doesn’t make my experience something to count on. I also had the advantage of having a driver on two occasions that made a phone call enroute to see which crossing would be faster at that moment.

The boat might be more fun … for some. But you will miss a couple of nice stops if you could do if hire a driver. Herceg Novi https://youtu.be/nNtT4Mh2ZTc?si=E8XAPiylEc7xlH0m and Perast, https://youtu.be/q2nckBnc7_M?si=CohK_4nsI6l7chEB . To be honest with you, the walled city thing is done so well with Dubrovnik that Kotor just comes up short. BUT, the trip along the Kotor Bay and the stops in Perast and Herceg Novi plus a short stop in Kotor make the trip more than worth the effort.

The old walled city of Dubrovnik—small as it is— is actually larger than the old city of Kotor. The OP might want to check on how many cruise ship passengers will be in port on the projected days of their visit.
www.CruiseMapper.com

Sure, but no cruise ships in Perast or Herceg Novi, so if you have to rough it for a few hours in Kotor ... such is life.

Am I kinda sorta close to your idea with the days listed below? All the RS people say to count nights. I still count days cause at night I’m sleeping. If you depart on a Friday, this has you home on a Sunday.

• 1 Depart the US
• 2 Arrive Dubrovnik ( 2 days ).
• 3 Dubrovnik
• 4 Drive to Kotor( 1 day there ) & Return Back to Dubrovnik (1.5 days)

If I am correct and you are thinking about going to Kotor and back in one day, then its possible, but a fairly long day. The boat hours don’t really work well for that, but might be okay if you spend the night. If you spend the night, do it in Perast. You will probably be happy you chose to do so. Most are.

Otherwise Stop in Herceg Novi on the way up. Plan on maybe an hour to get there and 2 hours there. Then on, bypassing Perast, to Kotor for lunch. Figure 2 hours in Kotor. Then heading back you stop in Perast, get a table at the Conte Hotel outdoor dining area that sits on the edge of Kotor bay, have a drink and wish you were spending the night. https://youtu.be/zYJcm2zlXA8?si=t0WCGbjVfOF8JY_q

If you do choose to spend the night then in Kotor do the cable car and/or drive up the scenic as all he…. P1 road to my favorite prosciutto, see it being hung, eat it, and a nice beer on the patio. Then get back to Perast in time to check in and get ready for dinner on the edge of the Bay of Kotor.

• 5 Dubrovnik
• 6 Drive to Sarejevo( 1 day ).
• 7 Sarajevo
  

I love Sarajevo. I love Bosnia almost as much as Montenegro. Unless you find a few more days, I would skip it.

• 8 Drive to Split and Havar( 3 days ).
• 9 Split
• 10 Split
• 11 Drive to Slovenia ( 4 days ).
• 12 Slovenia
• 13 Slovenia
• 14 Slovenia
  

Slovenia works so well with so many other countries in addition to Croatia. I would, if it were me, save Slovenia for my next trip to Italy and spend the time in Bosnia & Herzegovina and Montenegro because those are very difficult to pair with much in the future.

I think Montenegro and Bosnia & Herzegovina are the new Back Doors to Europe. Croatia was for a while, but the tourist found it quickly and now it’s on its way to becoming the new Cinque Terre.

I like travel videos to help plan my trips. There are a lot of Montenegro videos on this thread https://community.ricksteves.com/travel-forum/montenegro/podgorica-to-dubrovnik-by-car and some outdoor activities on this thread https://community.ricksteves.com/travel-forum/general-europe/no-place-like-rome

• 15 Back to Zagreb( 2 day)
• 16 Zagreb
• 17 Home.

Finally, I wouldnt drive. I wouild hire. Its cheap in Montenegro and Bosnia. I know know a good trip planner for the region that has all of the answers and costs.