Layout feature 1.9.1: use of 'use existing layout'

[ghost]

great feature! now, when trying the first time to use 'use existing layout' to get exactly the same layout I'm NOT able to edit it!?
I.e. I cannot see the layout like grid, row, column etc NOR e.g. open a HTML tag to be able to update the content.
I guess I miss something simple

well, in the meantime, I found a solution by plain 'clone' the CI!
Now I'm asking myself what for do I use the 'use existing layout'!?!
happy to receive guidance on how (what for) to use 'use existing layout'!
thanks for your time and help, ed