What can be done to make it less noticeable ?
I’ve been considering it but the seats have airbags. There is a warning not to use seat covers because of them.
It is possible to purchase seat covers that have a provision for the deployment of side airbags. You just have to look carefully to find this type of cover.
Is there a product which could be applied to the upholstery ?
Maybe. Ask at an upholstery shop where they do couches and such.