The following is my July itinerary:
Night 1: Zagreb (pick up car hire)
Night 2: Ljubljana
Night 3 & 4: Lake Bled (visit bohinj full day)
Night 5 & 6: Kobaird (caves visit en route to Rovinj)
Night 7-9: Rovinj
Night 10: Plitvice Lake NP
Day 11: 7 am visit to Plitvice np
Night 11: Sibenik
Night 12-13: Mostar (am visit to Krka?)
Night 14-16: (drop off car hire) split - day visit Trogir, full day boat trip
Night 17-19 ferry to Korcula
Early morning ferry to Dubrovnik p/u car hire at airport
Night 20: Montenegro
Night 21-23: (d/o car hire late evening) Dubrovnik
Day 22 morning lokrum visit; evening walking tour
Day 23 early morning walk walls, afternoon boat trip, sunset cable ride
Day 24: fly home
Day 12 drive from Sibenik direct to Mostar or stop in Krka np (after a full day prior at Plitvice np)?