Appending fields to the 2LIS_13_VD0ITM

I have noticed that in a modification of the extract structure MC13VD0ITM for the 2LIS_13_VD0ITM someone has appended some fields without the recommended ZZxyz naming convention. What are the implications? I have gone into the append structure to add ZZ to the names which I am able to save and activate. However when I try to add a field from the communication structure to the extractor (LBWE | Maintenance) and view the extract structure (se11) MC13VD0ITM the ZZ part of the amended name has been stripped. Why is this.

Not sure if it helps but although I am able to modify the append structures in the extract structure MC13VD0ITM, I am not able to edit/modify the extract structure itself. I get a message which asks for an access key. Any thoughts?

Thanks in advance for your help