Options for lower left side facial nerve damage since birth (had Botox & filler)? (Photos)

Thank you for your question and sharing your photographs. It is not really possible to do a proper diagnosis of your concerns in the photos.
The treatment with botulinum toxin is the most common solution for your problem and this is because of a variety of limitations for other treatments.
If you would like to explore the option of an end-to-side nerve graft from the strong side to the muscles on the weaker side, I would suggest contacting Dr Fausto Viterbo in Brazil as he has experience with end to side nerve grafting which is fed into the muscles on the weaker side.
The exact evaluation for possible success rate is complex and depends on many factors, so I would suggest first a virtual consultation to simplify the decision process.
The cross-facial grafting can be done as part of a face lift intervention if deemed to be an appropriate indication.

It is impossible to evaluate extent of your palsy based on photos; it seems to be rather limited, considering that you can accomplish improvement with Botox only?. Two sides of the face, paralyzed and normal, behave very different after face lift and may need more frequent educements with skin tightening then normal face lifts. In your current age, attempt of cross facial nerve grafting will not create much difference. In person consultation with a board certified plastic surgeon, face lift expert, who had some experience treating patient like you, is recommended. Good luck.