[notfed]

Success! Per your suggestion, I used Chordino plugin with Sonic Visualizer. I pumped in one of my old recordings and it showed me "B6" and "Dmaj7".

However, this was only so helpful. It would have been better if it showed me a fretboard and lit up which notes are active. Instead it just showed me e.g. "B6" which unfortunately has multiple implementations so I had to try many of the implementations across many capo positions, and it ended up being a "B6" that I don't even see documented in any chord guides, probably because I was using a capo. I was eventually able to find it by guess and check: randomly moving my fingers and capo around the fretboard then if it sounds close look it up to make sure it's "B6" in a reverse chord finder (i.e. oolimo.de). Still pretty painful for amateur me.

Perhaps the fact that a given chord has multiple implementations makes it impossible for the analyzer to know which one I'm using, but in my case I'm strumming all 6 strings so I suspect it's doable. Do you know if any tools can show the results as dots-on-fretboard? Or maybe I need a more thorough reverse chord finder?