Is it possible to pop-up an field for explanation of specific answers ons a Likert Scale (for example, if one selects one of the three lowest grades on the scale)? Because I do not want a required comment field for all the grades on the Likert scale, because if the given grade is high/good, I do not need an explanation.
Like to hear as soon as possible, thanking you in advance.
There is no built-in functionality that will allow you you to setup a pop-up window. However, you could use the hover tool-tip to build something similar. See the SurveyGizmo documentation for details – https://help.surveygizmo.com/help/hover-text.
The examples in the documentation show this function being used in the question text. You can add HTML coding to the response options, so it is technically possible to use this method. I think that the biggest problem that you will face would be informing the respondents that the tool-tips are available and will provide additional information.