Filters have a number of uses in OBO-Edit at the moment, and others will be added in the future.
Currently, filters can be used to restrict which terms and links are written to an OBO file. By specifying different filters for different files, it is possible to split an obo ontology into several different files. See The OBO Adapter for more information.
In the future, filters may be used to do automatic category assignment, modify the appearance of the Graph Viewer Plugin, or apply a similar edit to several terms.