The isometric center line and isometric object center tools work just like their 2D counterparts. Like other dimensions, isometric dimensions are linked to their objects if 'Create live dimensions' is checked in the CADdocument palette.

Isometric Center Line
Use it to show center lines of isometric objects or create exploded view lines. Click and drag to position the line, then release the mouse to finish creating the line. Hold down the shift key while dragging to constrain the Isometric Center Line to the current isometric angles.

Isometric Object Center
The object center tool determines the center of an isometric object based on its internal bounding box when flattened. Create an isometric object by drawing or projecting artwork. Select the Isometric Object Center tool and click on the artwork to create its isometric object center line.