Add data in repeat function

In my commcare database I have registered household(HH) and the HH participant in the repeat function. I have to add extra participant. Can i add extra participant even after form is submitted. Or can I add the participant from the Commcare HQ itself

You can't really edit forms after they've been submitted. You should be able to add a new participant case using the case importer, though.

i think you should consider, creating parent and child cases. Let registered households be parent cases and household participants be child cases. This way you can add members and achieve or close participants who are no longer available in the households.
https://confluence.dimagi.com/display/commcarepublic/Child+Cases

Thank you for the information. But I did the same thing. Where I have a household in a parent case and household participant in the child case. But the problem is I missed out some of the participant in the child case. Not I don't know how to insert the missed household participant. Do we have a solution for the problem?