Physics Builder Tools > Components > Extra Dimension Link

Extra Dimension Link
Use an Extra Dimension Link to include all items defined within an extra dimension defined in the Definitions Library, fro example, under the Components branch () as if they were part of the feature containing the link.
To add an Extra Dimension Link, first add a Component, then right-click Component and add it from the context menu.
Source Extra Dimension
In the Links from list, choose where to look for a certain property. Possible options are:
Definitions library. Lets you choose among the extra dimension nodes defined under Definitions Library>Extra Dimensions. Choose the extra dimension node from the Link list.
External resources. Lets you choose among the extra dimensions listed in an imported builder file under the External Resources branch. Choose the file from the Imported file list. The Link list contains all extra dimension nodes found in the selected file.
When the source extra dimensions has parameters declared, these are shown in the Extra dimensions parameters table. The value in the Expression column changes the parameter value for this particular instance of the link. Other links to the same source extra dimensions can use a different expression. If the source extra dimensions uses a loop parameter, the Loop parameter table appears. Enter the name of the dependent variable in the Expression column.
Attachment Selection
Choose an option from the Selection list for the attachment selection to use for the linked extra dimension: From parent (the default), Global, Operation, From definitions library, Top level entities applicable to parent, or Operation on sibling-feature selections.
For any choice, except Global, choose the Output entities: Selected entities (the default), Adjacent domains, Adjacent boundaries, Adjacent edges, Adjacent points, Mesh boundaries, Adjacent edges, Restricted to geometric entity types, or Restricted to frame type.
For Adjacent boundaries, select an option from the Restrict to list: All adjacent boundaries, Exterior boundaries to the domain selection, Interior boundaries to the domain selection, Exterior boundaries whose up side is in the domain selection, or Exterior boundaries whose down side is in the domain selection.
For Adjacent edges or Adjacent points, select an option from the Restrict to list: All adjacent entities, Exterior entities to the selection, or Interior entities to the selection.
For Restricted to geometric entity types choose the Allowed entity types in the table, Interior or Exterior.
For Restricted to frame type choose a Frame type: Material (the default), Mesh, Geometry, or Spatial.
Operation
For Operation, choose the Operation type: Union (the default), Intersection, Difference, or Complement. Then define the Input selections, and for Difference the Selections to subtract. Select options from the Output entities list as defined above.
From definitions library
For From definitions library, choose an option from the Link list and select options from the Output entities list as defined above.
Operation on sibling-feature selections
For Operation on sibling-feature selections, choose the Operation type: Union (the default), Intersection, Difference, or Complement. Then define the Input feature types, and for Difference the Feature types to subtract. Select options from the Output entities list as defined above.
Using Extra Dimensions in the COMSOL Multiphysics Reference Manual