How many days to spare for Kornati Islands?

[BartW]

Do they really have the connections/power to secure places at all town quays throughout Croatian Adriatic? Do you remember the name of the agent?

oops I misread your Q about power / connection ;-)

they have folks or connections everywhere,
fe, one of their agents (a young guy) did our clearance out of HR in Rovinj, while we were on the small nice town quay !
actually they did that while one of the offices (police or Harbour master don't remember) was closed !!! we were in a hury to leave because of weather forcast.

but for a berth, they can call around, and in HR they know each other, or they know their way...

for Hvar I know it is very tough,
during our return trip, (first week of august) they were not able to book the berth,
I went there with the tender and could see that the town quay was full of +35M boats.

we were anchored (FOC) in a nice cove approx 1nm NW of Hvar, (the cove with taverna Mareta)
I can strongly recommand that cove, we were there several times, and have seen deers ashore.