Hi, glad you like YARM! I hope it continues to be useful for you!
But what you're talking about is a different mod -- which I named Production Monitor -- that I actually started writing some time ago: https://github.com/narc0tiq/prodmon. I have this nice picture of it sort-of-working from two years ago: https://i.imgur.com/6guyabq.png (it's the one on the right, with "PM" before it; the info columns are: combinator name, type of signal, signal name, quantity, percentage (compared to biggest-seen value), rate of change, estimate-to-fill/depletion).
To a great extent, the ProdMon could even replace YARM (because you can read ore patch information from a miner directly), but because it's combinator-based, it would necessarily be later in the tech tree. Regardless, you can see why it's a fun little tool.
Sadly, as the commit history on Github shows, it hasn't really been a priority for me to work on it. Maybe now that I'm back to playing Factorio I'll take the time to continue/complete it, but I won't make any promises. Regardless, making YARM read chests is out of scope, and the YARM code is messy enough that I'd rather not complicate it.
Sorry to disappoint, but (assuming nobody else does it first), maybe keep an eye out for prodmon?