How can is increase the thickness of a slider line and increase the size of the dot. Had feedback from users that using slider is hard if you are not that dexterous! Any help appreciated
There is no standard control that can be used to change the dimensions of the slider elements. You can use custom CSS to modify some elements of the slider (see https://help.surveygizmo.com/help/slider-multiple#styling), but the height of the slider line is not one of these elements.
If manual dexterity is a problem for your target respondents, then you should consider using a different question type. Accessibility best practices usually recommend that slider type questions, along with other questions that require motion (drag-drop, grouping, etc.) should be avoided. See the SurveyGizmo documentation for details – https://help.surveygizmo.com/help/how-to-build-accessible-surveys#leading-practices-how-to-build-accessible-surveys