In 2D Drafting the toggle is in Tools->Assistants command group.
The location of commands change from Draft to 2D Drafting.
This allows you to create constraints such as 'connect' to an extension of an object. For example create a line that is connected to an existing line beyond the endpoint of the existing line.
Enable this option. Draw a line at an angle. Escape out of the Line command and start it again or just RMB to restart. Put the cursor on the line without clicking on it. Then move the cursor along the line and past one endpoint. Notice that you still get the indicator that the new line will be connected to the existing line. Click to start the new line. then click somewhere fot the other end of the new line. The new line will be connected to the projection of the original line. If you modify the original line, the new line will also change accordingly.
That worked what does the Extensions setting do in the intelliSketch Relationship window do?
Extensions is particularly useful when trying to dimension the inferred point beyond where a fillet has already been applied.
Design Manager Streetscape Limited
Solid Edge ST10 [MP0] Classic [x2 seats]