Is it possible to create a query

select function(value) from dual;

I know how-to create a function call,but I have no idea how to create the from dual part.

You may create a porocedure or function in your oracle schema to wrap the dual select.

If I would wrapp the function into other function the wrapper function had to be also executed in a select statement with a "from dual" select, doesn't it?

Not an expert in Oracle, but I thought you can create a stored procedure in your schema/package that would internally execute the select from dual. And return the values.

Yes, a procedure would work, but we have a lot of such functions from an legacy db.

I guess it could not be that hard to add some static class named Dual to the generated code which would write just create "from dual" statement.

You can add such class to the generated code. Since this have nothing to do with the catalog you are using nor the schema being used, then you won't need a template nor a generated code for it.