Since v4.0 Docxpresso offers you the possibility to create “global variables” that may be shared among different templates.
Global variables are tagged as any other variable with the only difference that they should be prefixed by DX-.
Admins may define their “global value” via the Settings > Global variables interface so whenever any template including a global variable is opened its value will be automatically loaded.
How to setup global variables in a document
You may see them at work in the following introductory screencast: