Unique ID widget: generate the ID based on a field selection

Is there a way to enlist the sequential unique id number only if a certain field is selected? A condition to only allow the sequential number to be used if a certain condition is met?

Unfortunately, there is no option to do that. The Unique ID widget is generated per each submission. I have added your suggestion to our feature request list.

You will be notified here if the option to generate the ID, only if an option is selected, is implemented in the future.