slicer should always indicate in the header if a selection has been made in a long list

The slicer should indicate if a selection has been made or not so that the user will know this even if the current selection(s) are not visible on the list (because the list is long).

As is, the HMI and thus the particular sliced data set is not always clear to the user and they are likely to be forced to unselect all slicer selections to establish any new configuration.

Optionally, the option to have a visual indication of 'slicer is using a subset' might be a configurable pararameter.