There is no built-in way to listen for changes to .env files to trigger a reload of the dev server.
This is especially frustrating when developing withing a docker environment where npm run server is the entrypoint. 
vue-cli-service serve --restart-on-env=true
This is especially frustrating when developing withing a docker environment where npm run server is the entrypoint.
I don't understand that specific point.
Also, I have a hard time imagining a scenario where I have to constantly change env variables. rebooting the dev server can't be such a hassle if it's once or twice a day or so?