To improve Microsoft Edge startup speed, we have developed a feature called startup boost. Startup boost keeps the browser running in the background with minimal processes, so Microsoft Edge will start more quickly when launched.
support.microsoft.com/en-us/topic/get-help-with-startup-boost-ebef73ed-5c72-462f-8726-512782c5e442
See also other microsoft-edge-startup-boost-tagged articles.