Yep, Sebastian is correct. Your lambda functions should show up under services. If you filter the services page by technology:Lambda Functions you should see them.
I have lambda functions that run as a cron, but they're not listed in services I guess because of the cron job within AWS that executes them. None of my other services communicate directly with these lambdas. Would still be good to get autotagging available on Lambda functions (the way we can autotag classic load balancers, and RDS databases).