How to convert an item from login to credit card category? Do I have to re-create the item?

Hi xandarar!

So how to convert the ones that need to be a specific category?

Items cannot be converted from one category to another (the only exception is changing a Password item into a Login item, since that only involves adding a username field). In every other case you will need to create a new Credit Card item from scratch.

And since we want to put some of these in a shared vault -- how to show the items aggregated by the category to which they are assigned? The aggregation happens fine in my personal vault -- Credit Cards, Banks, Drivers License, etc. But in the shared vault they are just all lumped together in one long list.

It sounds like in your Private vault you might have your items sorted by Category:

If you Shared vault has items sorted by Title, for example, it would explain what you are seeing. In that case just click on the "items sorted by" below the search field (as you can see in the screenshot), and select Category from there.