In the explore view of a dataset, a mark or highlight can be useful when filter or sampling method is applied. This will quickly help identify if default sampling or filtering was changed instead of clicking on configure sample.
Please allow me to explain with an example. I work with datasets of having millions records stored in Redshift/S3. For troubleshooting and validation purpose, I often apply filter to find out some phrases in text column. When the dataset is rebuilt with new set of records, view of the dataset appears as empty because it holds the filtering conditions which are not met with new records. With this view, I can think of two cases - dataset with no records and dataset with applied filter (If I manage to remember it).
Hence, if we could have a way to distinguish whether a dataset is applied with filter when we explore it, I think, we don't need to check by clicking on configure sample.