Let users save their Filter(s) they create in WebApp Builder.
This can be saved in cookie like the App State is saved for extent and layer visibility. This would be huge.
Also make Filter more discoverable, perhaps not buried in Attribute table. One button click from a widget tool in toolbar vs three clicks to go in to Attribute Table, then filter, then add filter. Trust me most people do not discover it unless directed to it. And sometimes even I forget I have a filter active. A badge (colored red vs blue-green to be color safe) in the Layer List by the layer name would make this more obvious.
Last, add a Filter badge to the layer list by each layer to toggle on/off and an All Filters Off button on the layer list. In fact, that could also be a place to locate the Filter button, I think that would be far more intuitive than in the attribute table widget itself. A little 'filter' button by the layer like in webmaps themselves. As well as an attribute table button like in the webmaps. Users do not notice the '...' button either.