Thank you Visio Guy for the prompt reply!
You should really consider that "buy me a beer"-app

Hmmm, the work space toggle is great so Visio remembers your window setup and all but it still won't do
what I'm looking for...
You could of course, after you have made your changes to the document, press Ctrl + W on every page and then save the document.
But that will be a lot of work if you have a large number of pages in the document... The best solution in my case would be
a tiny "on save" VB script that sets all pages in the document to a defined zoom level and goes to the "index page".
I have hardly any programming experience but maybe you can tell me if i'm on the correct path?
Private Sub Document_DocumentSaved(ByVal doc As IVDocument)
ZoomBehavior = visZoomInPlaceContainer
End Sub
/K