[Feature request] Extend placeholder support to multi-page diagrams

[bcm0]

That special field called "placeholder" does not work across multiple pages yet.
https://desk.draw.io/support/solutions/articles/16000051979-how-to-work-with-placeholders-

To test it just duplicate this page and change the cell's label.
https://www.draw.io/?url=https%3A%2F%2Fjgraph.github.io%2Fdrawio-diagrams%2Fdiagrams%2Fmetadata.xml

[joshualamorie]

I have some complex architecture diagrams with links between pages and I want to be able to add a semantic version to each page in case someone I'm collaborating looks at an individual page. There are a couple of options about where this gets stored:

1. Add global properties to the <mxfile> and access them in the same way as getting the globalVars.
2. Provide a mechanism to access the properties of a different page, e.g. %page/id,POhl_347sdf/property%. Of course some user friendly way of finding the page id would be needed.

[dylans-ingenuity]

Another bump for this feature request. We use M-Files as a document VCS, which keeps a plethora of metadata about each document. When creating a draw document, we have to manually add each meta item to each page of the document. This feature would save us a great amount of time!