How to add applications to the default panel?

[Achim Mildenberger]

Hello,

I hope the following question ist ok in this list.

Is there a possibility to include applications in the
default panel (plasma 5.4, openSuSE 42.1)? 

The reason I'm asking is, I'd like to include
things like dolphin and konsole in the default panel on a
student computer pool. If users mess up their panel or for
first time logins there should be some applications in 
the default panel.

I think the default panel is described in 
  plasma/layout-templates/org.kde.plasma.desktop.defaultPanel/contents/layout.js

In kde4 the following code worked:
tasks.currentConfigGroup = new Array("Launchers")
tasks.writeConfig("filemanager", "preferred://filemanager, , , ")
tasks.writeConfig("terminal", "preferred://terminal, , , ")

I tried this in plasma 5, but I didn't succeed.

Is there documentation about the layout.js available?
Or is there an example how to include applications (not widgets)
into layout.js?

Thanks a lot, 
Achim