Doing a quick eval of the suite…
Does the GoDiagram Suite fully support localization features of culture, date formats etc?
I can’t think of where there would be any…but are there any resources that need or are supplied localized?
Need to support German, french, Italian, Chinese etc.

GoDiagram Win (or Express) does not display any numeric, currency, date or time values.
The only place in GoDiagram Win (or Express) that has potentially user-visible strings are the default presentation names for transactions. These are given by GoUndoManager fields, and those names can be localized by supplying translations in resource files. And those names would only be visible if your application UI made them visible explicitly, for example by customizing the text of a MenuItem to indicate what the Undo command would undo.
I suppose there is a possibility that error messages might be seen, but of course your debugged and tested application would not generate any uncaught GoDiagram exceptions, right?