Filters can be found under the Settings tab, and are available for notifications like Reviews and Conversions:
Click the + button to add a new filter. You can be as creative as you want with these. Here are some examples:
You want to show only product reviews on product pages and not merchant reviews. You would create two Reviews notifications. One would include only product reviews like this:
and would be placed only on product pages, and the other would have a filter to include merchant reviews and be placed on the Homepage and other non-product pages.
You are having trouble with 5-star reviews containing some negative comments that you don't want displayed. Rather than going through and deleting the reviews one by one, you can instead identify some key words to exclude via filters:
If your notifications are not showing up and you are trying to troubleshoot why, try switching the include/exclude on your filter section. Sometimes it affects display even if there are no filters in place: