What would help smooth or soften the under eyes? (photos)

Thank you for your question and photos. Your photos don’t show significant volume loss, so you’re unlikely to benefit from a facial fat transfer at this time. Though you mention unsatisfactory results with Botox, the dosage and place of administration can play an important role in producing optimal results.
Properly administered Botox injections are an ideal solution for calming the overactive muscle contributing to the lines you’re referring to. Many patients are able to obtain their desired results by adhering to a regular injection schedule and undergoing touch-ups every 3-4 months. I recommend scheduling an in-person consultation with an experienced, board-certified injector who can assess your concerns and determine the best treatment option for you.

One drop of Botox immediately below your lash line in the middle of your lower eyelid should do wonders.
Some providers are comfortable injecting Botox in that area while others are not
I’m assuming your concern is the line right below your lash line.
In that area you don’t want volume. It will look wrong
Alternative would be a very conservative lower eyelid blepharoplasty with a very thin strip of skin only removal. Some providers do lower eyelid blepharoplasty‘s with muscle and skin removal. weakening the lower eyelid muscle can cause a premature ectropion.
Try to find the most experienced talented plastic surgeon, facial plastic surgeon or ocular plastic surgeon in your area for quality eyelid work.
My recommendation is to try Botox first since you already get treatment.
Best,
Mats Hagstrom MD