Well. after digging into documentation I've found that JBoss AS launch configuration could be edited at server page. But what's about standard location for configurations (similar to Tomcat configurations, for example)?
Is it problems with my jboss tools installation or "by-design"?
We've decided not to support server launch configurations disconnected from a server instance, so you won't find what you're looking for here. Much of our integration actively depends on a launch being THE ONE launch for a server.