Using function "[Object]'s Variable named [variableName] of type [valueClass] "

Hello, can anyone tell me how and for what this function works?

In a custom method with a list as parameter ,i am trying to do the next:

For each Object in list -> Object set property [CustomProperty] to [value]

For this i was wondering if i could use the function "[Object]'s Variable named [variableName] of type [valueClass]" found in Object as "other" functions.

Like the function [Object]'s part named [key]. But my problem is i can't drag it anywhere. Where should it be placed?


I am really stuck at Generics Methods with this, because i can't set an object custom property.

Hope my english was good.