Thanks for the write-up, a very interesting read!
Things that might reduce magic strings when using Quartz is using the typed configuration builders. There are integrations for ASP.NET Core and Hosted Services which both give you the configuration API which is documented quite well in MS DI Integration documentation . These actually utilize SchedulerBuilder from the core Quartz library so the strongly-typed builder for scheduler is available to without these dependencies too.
There's no built-in dashboard like you've stated, but there are options like SilkierQuartz if you want to plugin something.