This allows you to split a string into two pieces at a node point on the string.
Click on the required string and all the points in that string will be selected.
Now click on a point in the string where you want to Split it
Click on the 'Split' toolbar button.
The string will be split into two strings.
Note: When splitting a Lot string, you cannot split it at the start/end of the string.
You can see the start/end of the string by showing the string Properties and
Pressing the <-- or --> buttons to walk along the segments.