switch-wireframe-edge ("ste")

See this command in the command table.

To access this command:

Structure ribbon >> Edit >> Switch.
Display the Find Command screen, select switch-wireframe-edge and click Run.
Using the command line, enter "switch-wireframe-edge"
Use the quick key combination "ste".

Command Overview

Swap the linking off wireframe vertices from one arrangement to another within a quadrilateral. For example:

The command will become active and any wireframe edge can be rearranged during a command session.

Command Steps:

Display wireframe data with internal edges to be rearranged.

Tip: Show the loaded wireframe with highlighted edges before you run the switch-wireframe-edge command.
Select an internal wireframe edge (exterior edges can't be adjusted).

The arrangement of the internal edge swaps between possible arrangements, within the bounding quadrilateral.