As you model an object in Maya, each operation you perform creates a new node in the object's construction history. The Channel Box displays an object's node chain, and you can edit individual nodes until you delete the object's history. A node can represent any object attribute, such as the base mesh, subdivision modifier, surface extrusion, position, rotation or size. When you delete an individual node, you remove the associated property, but when you delete an object's history, you permanently apply all the current properties in the node chain.
Select "Object Mode" in the toolbar or press "F8" to change the selection mode. Click the object whose history you want to delete.
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Click "Display," point the cursor to "UI Elements," and then select "Channel Box" to display the currently selected object's node chain. The Inputs section of the Channel Box displays the object's construction history, and clicking a node expands that node's properties. If you only want to make a minor change to the object's history, you can edit the value in the text field next to a property.
Select a node from the Inputs section, click "Edit," and then choose "Delete Node" to remove the operation from the object's history. The Channel Box displays the oldest nodes at the bottom of the list, so deleting nodes deep in the node chain can have drastic consequences on your model. For example, deleting a subdivision modifier can prevent all subsequent nodes from affecting your model. To undo the deletion, press "Ctrl-Z."
Click "Edit" in the Channel Box, and then select "Delete History" to apply the current state of the node chain to your model. After deleting the history, you can no longer edit past nodes, but you can continue to edit the model by performing new operations.