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You do that by adding Project Parameters to Views to use in creating a new Project Browser Organization.
First off, they aren't actually "Folders". They are "Group By" headings. This is an important distinction.
To address your question we need to know how your browser is currently sorting your views.
In this example We sort our views by Discipline, then by View Type, then by Level (where levels apply).
For me to create a new Drafting Views (NEW) group I would need to create a new Drafting View Type and use those types for different views.
Properties for views (either built-in Revit properties or Project parameters that you create and apply to views) can also be used either for sorting and grouping or for filtering visible views.
Mostly, it's time to take a look at the associated help topics to learn how all this works.
Search for Project Browser, Project Browser Organization, and Project Parameters.
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Wait a minute...is this all you are trying to do?
Create a NEW Type then.