About the Trim Tool
You can use the Trim tool to cut or split a quilt or remove material from quilts to create a certain shape.
To access the Trim tool, select a quilt or a surface of the quilt to trim and click Edit > Trim on the Import DataDoctor tab.
You can trim quilts in the following ways:
At its intersection with another quilt
Along a datum plane
Against an internal two-sided edge or chain of two-sided edges
Along a datum curve or curve chain lying on the quilt.
In IDD you can trim any quilt except merged or combined quilts. 
Quilts that you can trim in IDD are represented by one of the following nodes:
An active or base-level procedural node.
An active or base-level component node.
A base-level surface leaf node or active surface leaf node of a combine node.
A surface subset of a component when the component is not a single continuous quilt, and the selected subset represents a quilt.
A leaf surface, component, or procedure node of a combine node that has no connections to the other geometry of the combine node, that is, a combine node that only represents a logical grouping, not a close connection.
In IDD the trim operation is not parametric. The trim operation does not result in the creation of a feature or operation that can be changed or deleted as in part mode. It causes a permanent change to the imported geometry. If the trimming reference is modified after the trim operation is completed, the trimmed geometry is not updated according to the change.
You can select which side of the quilt to retain for the Trim operation, or choose to split the quilt and keep both sides. If you keep both sides, one side retains its current location on the GTS tree, while the other is created as a new base node. This base node may be a single surface or a component, depending on how many surfaces make up the base-level node.