This option opens the Search dialog so that you can start an LDAP search for directory objects. The search scope (also called LDAP search base) is always the container which is currently selected in the LEX treeview panel or the object list. The technical details according to LDAP searches are outlined in the manual topic Searching the Directory.
You can start the search also when you use the Search button or when you press the hotkey CTRL-F.
If you see the Edit - Search option only disabled and grey, then this is maybe because your focus lays on the attribute list panel or you didn't selected a single container object in the object list.
Please note that the search dialog has two different modes: The simple search and the complex search. In simple search, just enter a search string, the directory is searched for objects which match this string with the most important attributes, for example the name or the mail address of the object. In complex search, you can enter any valid LDAP filter string:
If you open the dialog, the LDAP filter string is filled in from the Filter Factory, where you can construct and handle your LDAP filters - but you could also Construct here an LDAP filter and Save it to disk. Or you could Load an existing filter. LEX stores the appropriate filter files in the Profile and Filter Storage Path in the subdirectory "LDAPFilter" as text files.
You can read more about constructing filters in the according manul topic The Filter Constructor.
The results of your LDAP search is presented in an additional non-modal LDAP browser window:
You see no directory tree panel on the left side or the result list window, and you cannot change the base container (this is fixed to the LDAP base of your search) but it is a fully functional LEX browser window in every other sense. You can rename, edit or remove objects in this list, you can even create new objects (note the Base container at the top of the window - this is the container where the new objects would be created).
Or you can change the display of these objects, just if you were in a "real" LEX main window. Here is an example with the attribute lists shown for the currently selected object together with friendly name output for the distinguished names:
If you double-click an object in the search result window, you jump to the original LEX where your search was initiated, and the focus is changed to the clicked object - no matter in what subcontainer or subtree this object is: