EDITING: edit link attributes using filter ?

Hi,

How may I edit link attributes, first by selecting links with some  kind of a query ? For example, I wish to change capacity of all links where speed matches a certain criteria. 

Secondly, I am using default centroid connectors which have all attribute values as zero and this is reported as a warning after assingment. Does this matter in Cube Voyager? because different software treat this differently. I wonder what is the significance of this warning.

Thank you