Hi everyone, while this isn’t a built in feature with Unbounce yet, there is some fairly straight forward javascript that will allow you to set the value of a checkbox field. By using the ID of the specific option as a target for the javascript you can set the value with a single line of code:
You’ll need an instance of the above script for every option you want to change the value for. You’ll also need to add your own ID and value. The ID for a checkbox option in Unbounce is comprised of the label for the field and the label for the option separated by an underscore.
In the code above the checkbox field is labelled “untitled” and the option I’m setting the value for is labelled “choice_1” (It’s the default naming when adding the checkbox field to the page).
Ex. field label = "choose a plan"
option 1 label = "starter"
option 2 label = "Pro99"
option 3 = “Free”
The IDs:
option 1: #choose_a_plan_starter
option 2: #choose_a_plan_pro99
option 3: #choose_a_plan_free
You can set the value to anything you choose 
Pro-tip: Copy and paste are your best friends for this one if you have a lot of options
Hope this helps out a bit!