In Qlik Cloud/SaaS, when you're in Simplified Authoring mode, none of the items in the Properties panel are available for objects within containers. It says Properties disabled, whether you click on the container or try to click on the charts within the container.
This means that to use any of the features of Simplified Authoring, like the Chart Filters, you need to take the object out of the container, put it into Simplified Authoring mode, take it back out again, then put it back in the container.
Please would you consider improving the functionality for objects within containers, as it's really too difficult to work with containers in the new Simplified Authoring mode.