Please advise if this feature already exists and I just have not found it.
I have a table (new version of the table component) and it has a Summary row Add-on. In that I have specified a Sum over a column.
The table also has filters and what I notice is that the Sum which is calculated is always the entire dataset. Not what the user is seeing if a filter is hiding some of the rows.
This violates WYSIWYG fundamentally and seems like a less useful default behavior but I can imagine both use cases are appropriate at times.
I usually use a Query with JSON resource based on user filtering and then reload the table based on the filters so that the Summary row is always correct. I think your use case is valid but it may not be the one which is more common - in that tables are really meant to represent a data set so when interacting with it, there should be a refresh of sorts so the data, in reality, is "up to snuff" or "real time" My $.02
JSON SQL is also my best practice when the dataset isn't too large to download entirely.
However, the new Default Filters is looking pretty darn good as a replacement. I just updated on app from 2021 with the new table. It has 8 filters. I can now link 7 of those filters right in the table context:
I get that having the summary be a report on the "real data set" makes sense. But then, to be consistent, the filter mechanism should just be a UI that tweaks a where clause in the underlying query. Then the two facilities would be in harmony. One adjusts the data that enters the table; one reports facts about the data that is in the table.
Instead what we have at the moment is a filter tool that behaves like a first class query engine that, apart from the query that brings data into the table, it offers further refinement on what is visible. It's a query on top of a query. In this model a summary tool that counts hidden data does not fit.