The Disconnect constraint is used to break the connection between connected points.
To use Disconnect:
Select a connected line, arc, endpoint, or center point on the same sketch plane.
From the constraints menu, select Disconnect or directly select for sketch points. Note: Disconnect will delete any Coincident or Midpoint constraints for a selected point.
Learn more by watching the video below:
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Connected sketch points are shown with a filled center. For more information, visit States of sketch points.
for sketch points.