Visio Solution

I kinda like using Visio to play around with ideas.  I find it expressive enough for me to refine concepts into something that looks more like a software design.  What I can’t seem to figure out, however, is how to create a Visio Solution where I can have many sub-projects responsible for specific parts of my design.  I would be able to work with the Visio Solution as a whole, but toggle between different macro sets (sub files I guess) as I need them.    For example, I typically work with the UML software development templates.  These are OK for initial idea refinement.  What I also like working with is the Brain Storming templates (I like MindManager better for this however).  Both templates are “active” where Visio provides additional features to help manage, build, and validate your UML model or your mind mapping ideas.  However, you can’t use both active templates at the same time in the same file – I need to keep two copies of Visio open and toggle between the two as I refine my ideas.  It would be “cool” to be able to work in the same model “solution” instead of completely separate instances of Visual Studio.