Instead of using the [your-subject] for the 'subject' of forms in the wp admin side, can it be set to the actual input for the email subject field, in the instance that you've set a specific text-based subject?
For example, I have a client who has a site with 7 booking forms. Each subject uses the form's title, i.e. "Airport booking query", so the person inputting data never enters a subject, but my client know which booking the person needs.
I'd love to install Flamingo as a backup for my client, but cannot whilst it uses [your-subject] (which is set to be blank, as it's not used)