Originally suggested by Birk: It would be nice, if the <matrix>-element supported a parameter "initial" just like <spinbox> does. This is more difficult to implement than it might seem on first glance, in part due to the expand-as-you-type semantics of (user-resizable) <matrix>-elements. As a workaround it is already possible to initialize a (static) <matrix> by setting the tsv property.