Some days before, a new button raised in my AWS Console, simply named „AWS“. It contains a nice Tag Editor allowing you to find resources and tag them (but you shouldn’t do this by hand, automate it!).
From my point of view, resource groups are the much nicer feature. You can create a group and assign some custom filters to it like region, some tags and resource types. This group will show you all resources matching your filter including some extra info like raised alarms. Great at all to get a nice overview for your apps infrastructure. If you use AWS CloudFormation, nearly every resource is already tagged with a stack name. Fits perfectly here.