Advice on how to add the data in userdata of the subobject

I’m having a object of type “Dimension” inside which array of objects of type “Line” are present. The issue is we are able to add some data inside the userdata for the “Dimension”(object) but when I’m trying to add it for “Line”(children object),in userdata the data is not getting added. So just want to know that what I’m doing is possible or not. And if can somenone suggest way to add it

[object Object] in 3JS are like any other objects in JS. You just have to have the right reference.
You can use any name for the key.

xid is my user data added to geometry.