You can replace an operator by selecting the new operator from the submenu Replace operator of the context menu. This is similar to adding a new operator from the context menu instead of using the operator browser. When you replace an operator chain the inner operators will remain. Therefore, operator chains containing any children can only be replaced by other operator chains.
Removing the operator is even easier. Just press [Delete] or select the corresponding menu item from the context menu or the Edit menu. Figure 7 shows the icon for operator deleting.
You can use the arrows below the tree to move an operator up or down within its enclosing operator chain or wrapper. If you want to move an operator from one chain to another, you may cut and paste it.