Click the button "Activate scenarios for (form name)"
The checkbox Copy data from default scenario will copy all data from the default scenario to the new scenario.
You will now find the created scenarios under the Active scenario selector in the form builder.
When scenarios are activated for a form, the show/hide icon will be available on the form elements.
By clicking on that icon, it is possible to hide form elements for specific scenarios.

Important! When using scenarios in a form, remember to add a scenario selector element to the form as well.