IntelliJ Idea X adds quick navigation for Grails actions and GSP pages. Whenever an action has a same-named view, IDEA creates a gutter icon opposite to the action name. Click that icon and the corresponding page is opened:
As for going back, the GSP editor has a link to the appropriate action at the top:
rename for (I believe so) all wsdl entities (messages, porttypes, bindings, parts, etc)