As the subject suggests, when clicking once to set your origin point, then pressing and holding shift, the preview of your line should show until you click again on the destination point. That way you can see if your line is 'in the right place' before committing.
As the subject suggests, when clicking once to set your origin point, then pressing and holding shift, the preview of your line should show until you click again on the destination point. That way you can see if your line is 'in the right place' before committing.
I hope that helps