Hi @junior_diawara,
Welcome to the forum! If you have a moment, please introduce yourself in the welcome thread. Thanks for adding a profile photo as well!
You can set up your form to only create the entity if it is new based on the answer to the first question.
In the entities tab of your form, you would add a create_if column with an expression like the one below that can be true or false.
| list_name | label | create_if |
|---|---|---|
| point_of_sales | concat(${pos_name}, "-",${community}) | ${first_visite} = "yes" |
We need to add documentation for this "conditional create" case because I can't find a good link to share with you. There is a note about it in a very new XLSForm template on the "Additional columns" hint sheet.
For your other questions...
How do you define an attribute as the entity's unique ID (e.g. telephone number)?
We don't have a way to use other attributes like telephone numbers or other IDs as the unique ID of an entity at this point, but it is something we are thinking of supporting in the future.
I also want to add that in the next few weeks, we will have a new release of Central that will allow followup forms that can update entities, which seems like what you would ultimately like to use this form for. You will be able to have forms like this one that can both update entities and create new entities. That will involve just another change to the entities sheet that we will provide documentation for.