The controls for navigating the active View in the Slate Material Editor are similar to those for navigating geometry in 3ds Max viewports.
If your mouse has a middle mouse button or a wheel, you can use these controls to navigate the active View, even while the Select tool is active:
The Navigator window appears by default in the upper-right corner of the Slate Material Editor dialog. It shows you a map of the active View.
The Navigator centered on nodes in the View
The corresponding appearance of the active View
The red rectangle in the Navigator shows the border of the active View. Dragging the rectangle in the Navigator changes the focus of the View.
Moving the View border in the Navigator to change the focus
The corresponding focus change in the active View
The Navigator is most useful when you have a lot of material trees displayed in the active View. You can toggle display of the Navigator by a choice on the Tools menu.