Hello,
I have installed the 10.14 Mojave on my Mac with the default settings and it worked as the previous OS worked also.
After it I added the suggested code to my program:
TMSFMXDirectoryTreeView.Sort(0, True, True, nsmAscending);
and the result was in abc order.
I have tried it on Win32/Win64/macOS/Linux 64 and I think it does not use the SortOrder parameter:
The result was the same in the following cases:
TMSFMXDirectoryTreeView.SortOrder:=TTMSFMXDirectoryTreeViewSortOrder.tvsoDirectoriesFirst;
TMSFMXDirectoryTreeView.SortOrder:=TTMSFMXDirectoryTreeViewSortOrder.tvsoFilesFirst;
TMSFMXDirectoryTreeView.SortOrder:=TTMSFMXDirectoryTreeViewSortOrder.tvsoNone;