if just use hide=true to disable a application to autostart seems not very good. because in other desktop envirment will also can't autostart or even see this one. maybe can use such as X-XFCE-Autostart-enabled=false to do such job instead of hide=true, just like gnome does. and some XFCE own apps like xfce4-setting-helper add OnlyShowIn=XFCE by default, will solve many problems. sorry for my english. hope you can understand what i mean
No, we're not extending the standard for this. If you want to do something this complicated, you'll have to use a text editor for now.