Hi,
I'm just wanting to get some clarification from you about categories and your use of them.
Going back to the first post of this thread you mention adding a d:category custom property to your custom type and then after choosing a category in the create process it did not show up. Did you mean that it did not show up in the Categories panel in the document details page?
If you configure the property sheet to show your custom d:category property it should be visible in the Properties panel, is that the case?
For categories to show in the Categories panel the cm:generalclassifiable aspect has to be added, this is not done if you assign a custom d:category property to your type. This aspect exposes a property on your node called "cm:categories" which allows multiple values i.e. many categories.
This brings me to your last post, yes, you certainly can assign different categories to different documents, you'll just need to have separate rules for each category i.e. have a different condition for each type of document you want to assign a particular category to.
Could you let me know if my presumptions are correct, if not, please correct me.