On XFCE panel restart, unsorted "Window Buttons" panel items (aka taskbars) are reordered.

When using "xfce4-panel -r" to restart the XFCE panel(s), all instances of the panel item "Window Buttons" that use "Sorting Order: None" have their tabs reordered. This can be annoying if the user uses drag and drop to sort tabs.

Just a guess - maybe the only place this tab order is stored is in memory for the panel process which is about to be killed. If so, this probably means a fix will be slightly harder than it looks. The tab order will first need to be temporarily stored elsewhere (such as a temporary file, in the "xfce4-panel" process performing the restart, or in the windows themselves?) then reapplied after the panels finish reloading.