can I change it?
I find it tiresome: sometimes vlc is to the left, others to the right. This happens with other applications as well.
Can I sort them by application name instead of file name?
If I understood u correctly,open xfce panel settings and find there module which is responsible for showing opened apps in properties of this module change grouping type.
xfce-panel -p/--preferences(missing in settings window)Or
Right-click somewhere on a empty panel space > “panel” > “panel settings” (choose your panel if multiple) > tab “objects”. Edit “window buttons” or whatever object you have there (each has their own settings dialog).
Normally, there should be a “properties” on right-click on the respective object for direct access. But that’s missing in “window buttons”.
