I want to configure a part into different lengths (suppose 120mm and 150mm). Is it possible to configure on the same sketch? Please note that I am asking about the sketch, not the feature.
Yes it is possible and very easy, you edit the sketch you want to configure, then you click the dimension you want to be "variable" to the configuration of the part.
when the dimension propertyes tab on the right in the "prime value" section appears a configuration button. you must click the button and speccify ony this configuration, then you can changhe the dimension an the other configurations remains the same.