How can I set a filter that allows me to find someone who has experience with and/or specializes in taking care of senior dogs?
Unfortunately, there is no such filter. Try calling Rover Customer Support at [Edit: Rover’s contact options have changed. Visit the Rover Help Center at https://support.rover.com/ to find the phone number, help articles, or chat with the team] for assistance. Be sure to tell them that, as a customer, there should be more and better filters so as not to waste your time.
Agree with previous answer. Long ago, when I searched for a sitter for senior dog, customer service indicated that if the dog profile was filled out with breed, size, age, a search would list the most closely matched sitters (who also responded timely & posted daily updates) in top results.