This option can write attribute data from the clipboard directly into the currently selected object(s). This is the most interesting copy and paste feature of LEX. You can grab some attribute (or only a few single lines of a multi valued attribute) and paste it into another object - or even into several other object at the same time!
To copy attribute data into the internal attribute clipboard, you can use the menu option Edit - Copy Attribute Value or just press CTRL-C.
The Paste Attribute option is only visible in the menu if the following conditions are met:
This option cannot paste data directly into objects when the regarding data was copied into the clipboard in another application! Only attributes which where copied into the clipboard with LEX and the menu option Edit - Copy Attribute Value can be handled. If you want to paste external data into an directory attribute, you can open the regarding attribute editor and paste the data there.
You can read all about LEX's clipboard handling for attribute values in the according manual topic Copy and Paste of Attribute Values.