Creating the Patch Topology
You use the tools in the Patch Topology mode of the patch mesh Edit panel to create patches on the source surface.
By default, the patch mesh Edit panel opens in this mode.

The available buttons in the Create/Edit Patch Entities box are used to create, delete, and split patch curves. The buttons in this panel are “sticky” buttons. That is, once pressed, they stay activated until another button is pressed or the <Esc> key is pressed to cancel the action.
You can undo or redo any of these actions with the undo and redo buttons at the bottom of the panel.