checkbox field checked by default

Hi,

Thank you for this very useful plugin and for all your hard work for building it.
I am trying to use some checkboxes on the registration page and I couldn’t find a resolution to make the checkboxes be checked by default. Can you give me a hint on how do to this without altering the plugin files?

Thank you in advance for all your help!

https://www.ads-software.com/plugins/profile-builder/