Replace a list instead of item at index in nested list

I am facing confusion on getting the result i need in this replace item at index

i have 4 items in sublists in a list need to be replaced with lists…i know it is kinda confusing but may the pics can be more clear

A lot of thanks for your help,

i know it is very confusing, my condition is , i need not to have any arcs in my list so what i have done is took this arcs and divided it into lines, so what i need to do is remove these arcs (i have 4 in my whole list), and replace them with the newly created lines out of these arc divisions

i hope you can get my point and help me with this confusing issue

how can i really replace one item in a sublist by multiple elements…to remove the arc and put the 4 lines on its place

in my script, the 23 is actually the index of the arc inside the 29 list , it is not a value or item…it is index

image

I would use an if statement to replace arcs in the original list with the list of lines.

ObjectTypeOfOriginalList==Arc?
FunctionThatMakssLinesDrivenByArc:
OriginalList

IT would be the same issue, it is not about the condition at all its about the replacement