Hello there,
Sorry for the delayed reply.
We already received feature request with respect to GDPR but that feature was privacy checkbox in subscribe form, but as per your request it is double opt-in right? If so we planned this feature as a add-on(single opt-in/double opt-in)
For the next upcoming release(currently in progress) you will expect the following feature list(either one or all)
1. Privacy Checkbox in Frontend form(for quick you can make use of this option)
2. Manual Bulk Option to send mail
3. Template Structure support for Subscribe Form
We will let you know here, once we released the next update.
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