How to change sheet background (without any external code) in Qlik Sense like QlikView.
As far as I know, this is currently not possible with out of box functionality.
You can achive changing background through themes, altough themes aren't supported natively yet.
Check this: More Qlik Sense Themes (updated with 3.2)
Re: Access to CSS
You will have to go with a custom CSS theme to achieve this. The links which Undergrinder provided should help you achieve this.
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