Currently the group plugin with cloneable set forces at least one entry to display when adding a brand new post (for example). This causes an issue when one or more of the fields are required. We would like a way to have zero or more values in the group but if the user adds a value, they must fill in any required fields.
I think if you mark a field required, the browser will force you to enter a value. It works per field, which means it doesn't depend on values of other fields. So no matter that field is in a group or not, if it's required, it should have a value.