A few customizations that can be performed by DevOps are as described.
The Windows Forms control allows the Window Forms-related customization. See Windows Forms Viewer topic and the Win Viewer sample for details.
You can customize the WPF Viewer by applying themes. See WPF Viewer topic and the WPF Viewer sample for details.
See the JS Viewer API to learn about the customization possibilities of the JS Viewer.
For example, you can change the viewer toolbar in several ways:
You can also change the position of the sidebar panes such as search, parameters, etc.
You can turn on/off almost all elements of the Report Explorer and script/preview tabs.
See the WebDesigner API to learn about the customization possibilities of the Web Designer.
You can change the visibility of many designer components, such as group editor, report explorer, toolbox, tabs, buttons, and more.