Here is an idea from one of the editors who edits using scenario editor of aoe2, is it really possible?
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MLC8896
Age Insider
10d
Funny, I just made a Request post about something to do to make this possible.

The simple thing to do would be to create a second Variable option, that would remain true for all scenarii as long as they are bundled together within the same campaign file via the Campaign Editor.

Here it is:

"Basically make a variant of the current Variable system where the Variables you set in one scenario remains true for any other scenario as long as these scenarios are linked within the same campaign through the Campaign Editor.

I don’t know if that’s something possible at the moment, but this simple feature would take Campaigns in a whole new dimension as choices you make in one scenario could basically bring consequences in later scenarios of the campaign, and increase dramatically the options of the player.

Let me know what you guys think of this."

I do believe it is something we can make happen. It would be just crazy all the options it opens for single player content… And think of replayability…

OMG.........