This function is used to change of the content of a list at a particular index or to insert a new item at a specified index. Insertion effectively moves every item from index onwards to the right. The index is zero based and counts from the left. ie. 0 is the first element, 1 is the second, etc. Negative indexes count from the right. ie. -1 is the last element, -2 is the second to last element, etc. An invalid index will result in nothing being changed.
If the list delimiter resolves to be empty when the action is executed, a default (\~) will be assumed.
All text fields may contain any of the escape sequences described in Escape Sequences.
Note that where running stepwise the function is only performed once if the list is in a named variable.
The action test state will be set to true if the index was valid for any processed files.