From an open Cmap:
You can provide more detail about a subject by putting Cmap items inside of a nested node. Nested nodes are useful when you want to add extra information, with quick accessibility, to an expandable concept. To create a nested node, begin with a selection of Cmap items you want to include in the node (You can select all Cmap items by pressing Ctrl+a). Select Tools, then Create from the Nested Node sub-menu.
Now, a newly-created nested node surrounds, or nests, the Cmap items you have selected. The nested node initially appears in its expanded mode with a set of arrows on the right.
You can collapse a nested node to hide the information it contains. One method of collapsing a nested node is to click a clear portion of the node, select Tools, then click Expand from the Nested Node sub-menu to release the checkmark. (You can return to expanded mode by applying the checkmark to the Expand sub-menu item. Also, an easy way to expand or collapse a nested node is to click the set of arrows on the right of the node.)
A nested node enters label mode once it is collapsed. In label mode, the nested node may be labeled just as a normal concept would.
Cmap items located inside nested nodes may be arranged just the same as if the items were located in their own Cmap. To reveal other Cmap items that may be covered up by an expanded nested node, return the node to label mode. (To add existing Cmap items to a nested node, hold shift while dragging the selection of items into the node.)
After returning any expanded nested nodes to label mode, you can clearly view the main ideas of a Cmap.
You can remove one or more child Cmap items from a nested node. To detach a selection of child Cmap items from its nested node parent, select Tools, then select Remove from Parent from the Nested Node sub-menu.
Now the nested node only surrounds those Cmap items that were not chosen for removal.
You can automatically remove all Cmap items from a nested node. To detach all Cmap items from a selected nested node, select Tools, then select Detach Children from the Nested Node sub-menu.
Now all contents in the nested node will be removed, and the nested node's label appears in a separate concept.
You can combine the contents of multiple nested nodes. To combine the contents of multiple selected nested nodes into one nested node, select Tools, then select Merge Nodes....
From the "Merging Options" window :
You can decide in what way you want to merge Cmap items from selected nested nodes. Concepts and Linking Phrases are examples of Cmap items that may be merged. Also, nested nodes are considered concepts for merging purposes. In the illustration below, only concepts are able to be merged. Linking phrases were not inside the original selection of nested nodes to be merged, so they appear grayed out. Selecting the Only merge if node labels match option restricts merging of Cmap items to only those items that have the same label. Click to fill or clear the checkboxes, then click Ok to merge selected Cmap items.
In our example, the selected nested nodes have now merged into one nested node. The way that nested nodes merge depends on the labels of the nested nodes selected and on how options are set from the "Merging Options" window.