...select a Lava construct for insertion by clicking an associated tool button. You need not know its syntactical structure in advance: LavaPE will insert a "template" of that construct for you which exhibits its syntactical structure and contains placeholders for nested constructs that you may insert subsequently.
Optional parts of a construct can be deleted or reinserted if required.
The description on this page isn't the strongest, but the idea of a structural code editor is very powerful. The benefits are clear: no syntax errors, customizable syntax representation, easier provisions for refactoring, etc. Bringing this design into the 21st century with modern search tools, UI paradigms, and shininess could be quite valuable.