Form Conditional Logic

Sounds like you just need to have conditional visibility based on the boolean field.

If the boolean is true (means the user ticked the box), you show an entry that is not required.

If the boolean is not true (not is false, which doesn’t cover the case when the boolean is empty), you show an entry that is required.

But does the form get submitted in that case? If you want to allow a user to not complete a form and go back to finish and submit it later, use a custom form.