In Windows 11 there is a Taskbar setting (under Taskbar behaviors) "show seconds in system tray clock" but since Taskbar had to be disabled so it doesn't interfere with DisplayFusion (DF) it would be nice if DF at least matches Taskbar's functionality. Or is there a DF setting to show seconds on all clocks on all taskbars?

Never mind: found it under Advanced Settings > Clock Text Date Format (all taskbars) and then use HH:mm:ss\ndd/MM/yyyy