If you load up the Language Designer app, you can import a SyntaxEditor for WinForms dynamic language XML file there. That will convert it over into a .langproj which can be edited in the Language Designer. Then you can choose to output a .langdef file or language class files. Basically, once you import the WinForms XML file in, you can refer to the documentation for help.
The main difference between the WinForms and WPF version in this area is that syntax languages in the new framework are just generic service providers (as opposed to having special language classes like DynamicSyntaxLanguage). There is an ILexer service which is a lexer for the language. DynamicLexer implements ILexer and can be used to load up .langdef files that are output from the Language Designer.