To easily edit docs inside of a running eXist DB
Two step process: (1)add a data source; (2)add a connection
1.1) Go to Options -> Preferences -> Data Sources
1.2a) Add a new data source in the top panel (titled Data Sources)
1.2b) Type: eXist (add the following driver files from the WEB-INF directory of your eXist instance: exist.jar, ws-commons-util-1.0.2.jar, xmldb.jar, xmlrpc-client-3.1.3.jar, xmlrpc-common-3.1.3.jar)

2.1) Choose the just-created Data Source
2.2a) Add something like this to the XML DB URI field: xmldb:exist://localhost:8080/exist/xmlrpc
2.2b) Add login info to User and Password fields
2.2c) Provide an internal path to your collection (like "/db")

Use Window -> Show View -> Data Source Explorer to browse the db.