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

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

This would be a greatly appreciated feature for me! And I suppose this could be possible since there are already placeholders across pages like %pagecount%.

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.

This feature would be a game changer for our team. We use diagrams.net for most of our technical drawings, but it is currently cumbersome to update version numbers, author details and other global document values across each page.

Please!!! I'm needing this like wather!!!

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!

Another bump for this feature request.