If you happen to be using AWS, GitHub, and Slack, we at DoorDash have developed lots of goodies for streamlining things. We have secured our Jenkins behind our VPN, created load balanced Jenkins clusters, built a shared Groovy library for all of the Jenkins behaviors that are useful for each of our microservices, implemented a Flask app that receives each of the GitHub webhooks which starts pipelines instantly (rather than git polling), setup Okta integration, interfaced with our internal secrets store, and implemented a way to map GitHub users to Slack users allowing us to Slack message people when they are mentioned in GitHub (when their PR's receive LGTM's etc.) When new microservices launch, Folders automatically appear in Jenkins configured correctly for the service's pipelines.
If any of this sounds good let me know, maybe we open source some of our work. I love working on Jenkins and am happy to help advise you on how to scale, secure, demystify your own Jenkins setup. Links on my HN profile page.