The shell command options can be completed in the shell by hitting the TAB key after the leading --. For example, hitting TAB after stream create -- results in

dataflow:>stream create --
stream create --definition    stream create --name

If you type --de and then hit tab, --definition will be expanded.

Tab completion is also available inside the stream or composed task DSL expression for application or task properties. You can also use TAB to get hints in a stream DSL expression for what available sources, processors, or sinks can be used.