Answered
How can I write a script for set left indent?
In three cases as below:

for example:
left indent:8mm; first indent:0mm
left indent:0mm; first indent:8mm
left indent:8mm; first indent:-8mm
How can I write a script to tell Indesign, wherever the text indent is, each time when I run the script once, the text can put just a step rightward, and “one step = 8mm”.
Please!