Whenever you update a blueprint make sure to also update the code block in the original post too, because that’s what gets used when people import your blueprint into their Home Assistant.
This doesn’t show all of my things. When I go by area, it only shows 7 areas and if I pick one and expand it, it does not show all the items in that area. When I try to search by device, it again does not list them all. Entity also does not list all things.
That depends on the domain of the selector, this blueprint is made for lights.
I have not tested it but maybe you can add multiple domains ?
You can read about it here: https://www.home-assistant.io/docs/blueprint/selectors/
There was a recent report of a way to do it but, upon further investigation, it turned out to be a bug and not an undocumented feature. The technique generates warning messages and the selector’s menu doesn’t always list all of the available entities (like I said, more of a bug than an undisclosed feature).