IMPORTANT: Not "Dependent Fields".
Please see Gravity Forms' conditional logic functionality for example: https://www.gravityforms.com/form-conditional-logic/
At present, HubSpot "Dependent Fields" can serve new form fields based on a selection made in a previous form field.
"Conditional Logic", however, serves different form field options based on a selection made in a previous form field. This is an important distinction as it requires only one "Property" for the options, regardless of the initial form field selection.
If I'm not clear, here's an example:
Property 1: Location
Property 2: Duration
User selects from a Location dropdown. Location options are "Madrid" or "London".
We only offer "4 Weeks" and "6 Weeks" for "London", but offer "4 Weeks" or "12 Weeks" for "Madrid".
"Dependent Fields" will serve Duration upon a Location selection, but all options will be shown, even though we do not offer all Duration options for both Locations.
HubSpot recommends we create a new "Property" for each Location. This is not feasible when there are many Locations.
"Conditional Logic" simply serves the appropriate form field options based on the Location selected. So when selecting "London" the options shown would be "4 Weeks" and "6 Weeks", and for "Madrid" only "4 Weeks" or "12 Weeks" would be shown, but they would all populate the same "Property". Duration.