dotfiles/powerline/config/themes/vim/cmdwin.json

{
	"segments": {
		"left": [
			{
				"type": "string",
				"contents": "Command Line",
				"highlight_group": ["file_name"]
			},
			{
				"type": "string",
				"highlight_group": ["background"],
				"draw_divider": false,
				"width": "auto"
			}
		]
	}
}