How to use global diagram properties across multiple pages

[Martin Newman]

I've added "global" properties (as per  Blog - Placeholder labels respect scope) by making sure nothing is selected and adding key/value pairs. I can use them wherever I need to automatically change text on the same page without issue, but if I try to use them on another page it doesn't work. The "Edit Data" dialog for the second page shows no properties.

How can I make these properties work across pages?