This option is a convenient way to configure the attribute filter which is applied to attribute list panel in the LEX main window - or in a stand-alone atttribute window which is opened after the fiter configuration.
In the default configuration, LEX shows all attributes that are returned from the server. However, you can configure a filter which is applied to the request. So you could choose for example that only specific attributes are shown in the list - regardless of what object you examine. Or you could choose to exclude some attributes from the display because you are connected with low bandwidth to the LDAP server and want to see only what you need.
If an attribute filter is active, the Set attribute list filter button is blinking to attract attention to the fact that maybe not all attributes are shown in the current list. Please note that the attribute filter works only if there was a correct schema evaluation for the current LDAP server. Additionally, this option is only visible if the application focus lays on the attribute list panel.
To activate and configure a filter for the object list, you normally use the Set attribute list filter button or the menu option Tools - Options - Attribute Filter. In this case, the Attribute Filter dialog is shown:
With our menu option Filter Display for this Attribute, you open the Attribute Filter dialog and the attribute list in this dialog is pre-filled with all the attributes which are currently selected in the LEX main window!
Another, faster way to put all currently selected attributes into a filter definition: Open the context menu directly in the attribute list (right mouse-click) and use the option Filter Display for this Attribute.
Please remember that the attribute display could also be affected by the configuration for unused attributes. The attribute filter specifies generally what attributes LEX shows in the list, with the Show Only Attributes That Have Values button you configure in addition to that if the empty values are visible or not. So both settings are mixed together- what you see is an intercetion.