The Add/Edit modal for a table is controlled by the table configuration, not just by creating any form view in the data class. If you only see Edit, it usually means the table is not fully configured for Add or the modal view is not being created in the location/type that the table expects.
Please check whether the table has Allow add/edit/delete enabled, and also confirm whether your property is embedded data or data reference, because the supported modal-view configuration differs between those patterns. For data-object-based tables, the form view is usually created under Data type > UX > Other views > Form and then selected in the add/edit modal setup.