I did try the latest TMS FMX UI Pack on 64 bit Windows 7 / 10 and 32 bit Windows XP, but nothing changed.
The result in abc order, but the directories are not before the files.
I am using the following code in the FormCreate event: TMSFMXDirectoryTreeView1.SortOrder:=TTMSFMXDirectoryTreeViewSortOrder.tvsoDirectoriesFirst;