That would be nice, but the problem is that it’s not possible to know that number in advance to show it. You must apply the filter to get the actual number at that moment. Records can be added or deleted at any time, and by other users.
BUT! On the other hand, I can implement something really close in my KTL (Knack Toolkit Library) that would show that last number of records found for a given applied “User Filter”, when you hover over the button. That would be a close indicator that could have some usefullness.
FYI, the User Filters are buttons provided by the KTL that allow you to name any custom filters you create and save them as a button for quick retrieval. Much more versatile than the presets that only allow one field/value pair.
Go see it here: KTL on Github
It’s still in pre-release, but very functional. I use it in two industrial projects where the company tracks their production and manage sales.
If you’re interested in such a feature, let me know - and most of all… KTL is 100% free.