The WPF Theme Editor does not support the DevExpress WPF Controls 18.2 or later. Use the WPF Theme Designer tool instead.
The Product Browser allows you to navigate through DevExpress products to select the one whose visual presentation you need to change. It displays a tree list, which enumerates products supported by the Theme Editor.
Once you have selected a product, the Theme Navigator shows a corresponding product view allowing you to navigate through the displayed UI elements and edit their appearance.
Specific products have several views with which they can be displayed in Theme Navigator. You can expand such products in the Product Browser to access a list of available views.