I am talking about September 2019 here. Thanks to everyone for your help. Any serious objections or comments on anything that follows here will be very welcome.
This first paragraph to acraven: Thank you. I should like to learn more about trains in Romania. The Interrail Pass map really does show a much denser train network than any other Balkan country, purportedly representing running trains (which may or may not be the case, of course), but certainly not just tracks. But how can I learn which of these are genuinely operative?
My feeling now is that I should not have trouble getting to Ljubljana, Zagreb, Belgrade by train. From there I can take the famed railway to Bar and bus around there for a while, perhaps returning, for want of better, by the same train to Belgrade.
Belgrade-Sofia seems to have just one train per day, direct until September 16 (not sure if I can make that), otherwise with two changes. I do want to visit Sofia if possible.
Do I have any chance of getting up to Romania from Sofia? I will study the possibility of continuing on to Thessaloniki by train, at latest when (and if) I get to Sofia. As Laura puts it so well: “Staying flexible and re-confirming schedules as you go is a key strategy in this area.”… My philosophy now is that wherever I get to, I can always go back the way I came. I hope this is not too optimistic!
Regarding the Balkan Pass, I already have a two-month Flexi Interrail Pass, which should cover all of the former, no?
My reference to Turkey was based on a ferry from Athens, if ever I get there… I have now given up the need to get to Greece in my mind.
Do I have any chance of getting up to Romania from Sofia? Is it impossible to continue on south by train?