Our users are having some UX/UI issues with the calendar filter. Namely, some of our users have had the Event type filter on without realizing it, which causes some events to not appear in the calendar view (without them knowing why).
There does not seem to be anything to show you when you have a filter on. Does the plug-in offer anything in this regard, so a user can easily see when they have filters applied?
The filter bar keeps the current filter checked or marked in the filter bar itself. Beyond that we do not have any features to show what is currently being filter.
There is always room for improvement if you think that is something you would like as a feature I encourage you to visit our User Voice Page and either upvote an existing request or make a new request there.