This is Horizontal trendline-drawing tool.
Press the button and a horizontal trend line appears.
All lines can be extended or shortened.
All lines can be hidden.

To delete them all, set [All delete] to True and apply indicator again.
Then [All delete] back to False.

I am not very good at analysis horizontal level.
What are you careful about when you draw horizontal line?

Tips:
If the line is no longer horizontal, press [Ray+] button. All line will be re-set with reference to the left edge.

Tips2 :
Renaming a line prevents it being erased.