There is no easy way to have optional parameters on an adapter

Added support for optional parameters.
These parameters can be defined in the operator parameters table with no default value and with Not Null and Not Empty properties unchecked (in the parameter detail form).
Then, in the template, an optional parameter should be given as:
#optional("label", $param)

For example:
#optional("--maxit", $maxIt)
assuming that $maxIt parameter has been already defined for the adapter.

Then, in the execution dialog, if this parameter has no value given, it will be omitted from the generated command line.