(Later) - Yesss! That worked. I marked the folder names using left mouse button to select the first then the left button + CTRL to mark the others. Clicked "Synchronize" and marked "Selected files" and it did exactly what I wanted it to do.
Thankyou so much.
What a superb program this is. Everyone who uses it should make a donation!!

Thankyou Martin, I need to add more photos and txt files today and will try that on some different regions (pontos, phrygia and macedonia).

So go to greece in both panels and select the subfolders you want to synchronize (it's enough to select them in one of the panels only).
Or are there more top-level folders (in addition to greece) that you want to synchronize?

Sorry, I am probably not making myself clear.
When I select the /greece/ upper folder and use Synchronize, of course it synchronizes ALL the 120 sub-folders from greece/aeolis/ to greece/zeugitana which takes a long time (ca 15 minutes or more because of the large number of files in all 120 subfolders).
But if I have only updated (added files to) four or five of those subfolders, I want to limit the job to synchronize only the folders I want it to check, not all of them.
Of course I could select the subfolders one after the other, but I thought I could tell it, "synchronize only greece/thrace/, greece/moesia/, greece/macedonia/ and greece/illyria/"

But that's what it does, doesn't it?
Note that "files" quite often means "files and folders" (and it does in this case).

Hi Martin
I already use the Synchronize system but the "selected files only" wouldn't work for me, because I need to select entire folders to be synchronized, but not ALL the folders under e.g. /greece/.
So how would I make it synchronize, (for example) the folders and contents under
/greece/thrace/ and
/greece/macedonia/ and
/greece/illyria/
and not all the other /greece/,,, region folders ?
? Could you tell me what such a mask would look like and where it would be added ?

You can use Selected files only option:
https://winscp.net/eng/docs/ui_synchronize

Or you can explicitly exclude folders, that you do not want to synchronize, using a file mask.

Hi Martin and everyone
I have several folders for my (ancient coins) website, each with several hundred sub-folders. I add files (images, thumbnails, text files and the html files to sub-folders in alphabetical order about once a month but never have time to do them all in one session. The main folders are named, e.g. greece, ric, byz, brit etc and each of these folders has a large number of sub folders (under "greece" for example, there are acarnania, arkadia, aeolis, apulia, arabia etc...) and each of those sub-folders have their own city folders with two html files plus all the images and text files for coins from that city.
Tonight, for example I added images etc to the ric/ sub-folders A to D.
I do a synchronize run but because there are so many sub-folders for about 76,000 coins - it can take a long time.
Is there a way I can tell the program to synchronize only certain sub-folders ? e.g. just to synchronize acarnania, aeolis and arabia (using the above examples)