I would like to create a checkbox type custom field that has nested options under certain options. For example, I might have a checkbox custom field called vehicles. It has 2 options (truck and car). If a user selects "trucks", I want a new subset of checkboxes to appear under "truck" like "red truck", "green truck", "blue truck". If the user selects "car", I want a new subset of checkboxes to appear under "car" like "red car", "green car", "blue car", etc.
I tried creating a separate field and hiding/showing the separate field based on the option(s) selected from the parent checkbox field, but users want the sub-groups to appear directly under the option and not in a separate "field".