1. A method of filtering network device configuration files by a network management system, the method comprising: storing a set of design filters in a storage device by providing at least one input screen via a graphical user interface; receiving a design filter script via the at least one input screen, wherein the design filter script includes primitives for searching lines and paragraphs in the network device configuration files having specified attributes; converting the design filter script into an executable design filter, the executable design filter configured to implement the searching when executed; and storing at least one of the design filter script or the executable design filter in the storage device; receiving, via the graphical user interface, user input identifying a selected design filter from among the set of design filters and selecting a plurality of network device configuration files; applying the selected design filter to the plurality of selected network device configuration files to produce filtered results including filtered results for the plurality of network device configuration files; and providing the filtered results via the graphical user interface for display on a user display device, the filtered results provided via a screen having at least two windows arranged side-by-side within the screen, wherein each window includes the filtered results associated with one of the plurality of network device configuration files, the filtered results displayed as at least one of individual commands or command lines from the plurality of network device configuration files.