What service/app?
Discussion
Imatag.com
There are other ways to do it too. You just have to search the term to learn about it.
I don't see the reply I left on primal. So here.
Imatag.com
They are a service.
Do yourself the favor and search the term Steganography.
There are a lot more ways to implement it and you can do it yourself, and there are even ai services now that can do it for you.
What they can't do is paint you a custom piece of Artwork from my head and tablet, as I can, that will forever contain your seed words.
Thanks for the tip, I'll check it out, sounds useful!
Btw, I do see both replies