Old topic, but why does the A key not work for me to toggle between a line and an arc? Is there a setting I don't know about?
Check your Keyboard shortcuts to see if the A key has been assigned to another function.
I have mine set to Appearance
It appears to be. I just reset mine to that toggle and it works.
It will only work before you move the cursor from the end of a line or circle. If you move the cursor before using the A key, the next command will have been activated.
Line tool > click > move > click > A key > gives radius from end of line.
Line tool > click > move > click > A key > gives radius from end of line > A key > gives another radius.
Line tool > click > move > click > move > gives another line. The A key will have no effect till end of line is clicked.
To answer your question though, simply move the cursor back over the endpoint and pull away in the direction you need. That should take care of it.