I agree, this is not user discoverable or intuitive. Too easy to forget it's on, too. It would be great if they would highlight the layer name in the layer list a color or something, or superimpose a badge on it, and simultaneously let you deactivate the filter from the layer list, perhaps a prompt from an on-hover. Also, I noticed a bug. If you click a layer that's filtered it highlights it blue. OK, well I closed that. It says highlighted. Even after closing the attribute table and closing it in the attribute table. Only way, was to reopen it, then hit Clear Selection. If I close the layer in the layer list it should clear the filter, I think, or at least it should be by default, and perhaps programmable otherwise. I also agree it should have a Clear All Filters button.
But it's fantastic, nice overall interface design. Also I wish you could use select from the top to bottom record to select all records but it appears if you have to scroll it forgets its place so you can't select hundreds of records that way. That's a plain attribute table thing but something else I noticed just know. This should work, and there should be a Select All. So that a user could export all records in the table, if it is a lot. And also to display them. Because one downside is the Filtered records don't show if there is scale dependency. Selection is an easy way to show them and would work for me, but you can't select more than a handful of records.