Recently you changed the startup, and I like the Viewport filling, but I don’t care for the new plane and the Environment Sky colors are hard for me to see.
Could you make an option that if you create a scene the way you like it, somewhere there is a ‘Make This Default’ scene.
My steps for a new scene now is delete existing plane and change the colors of the default light and sky. I usually add Physics Scene and Groundplane, so that would be nice features if there was a way.
Perhaps others will find this useful.