Not sure about apps since I don't use any, but on the website versions of both Lemmy and Kbin instances, there is a link either on the sidebar or at the bottom of the page that says Modlog. It defaults to showing you a global list from all federated instances of all the most recent moderator actions. On Lemmy instances the moderator's names are hidden but on Kbin instances it will always show you Moderator > action taken.
(edit: on Lemmy instances only): There's also a useful search feature at the top which lets you look almost anything up.