I tell you, that you can assign rights to your users.
For example, go to component options, tab Permissions.
You can configure permissions for registered users, author, editors and so on.
Ie you can assign ACL group to your users. For example, author group. By default it configured to create + edit own.
In the result - you can create anything, but edit only your own placemarks (because placemarks have creator reference)
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