my question might sound a bit off but how to make this thing ? i'am not sure what is called i'm sorry
It is a widget or combination of widgets. You can use the code below and then position it at that point.
SizedBox(
width: 40,
child: Divider(height: 3, thickness: 3, color: Colors.grey),
)
That is the quickest solution I could come up with. Alternatively, you can use a Row(), then look for such a line icon and have it as the child. Of course, set the crossAxisAlignment of the Row to center.