I also don't love the conventional handwritten aesthetic you often see for jazz fonts. For a project I've been working on, I ended up pulling the handful of chord symbol glyphs out of MuseScore's Leland Text font and adjusting them for use in the UI since I couldn't find a suitable option out there.
For just chord analysis, there's "Harte notation", which is meant to be unambiguous representation of the notes (https://ismir2005.ismir.net/proceedings/1080.pdf). That obviously doesn't get you all of the additional information necessary for engraving and full representation of the music, but there are research datasets available using it like https://github.com/smashub/choco. I've also used the https://github.com/MarkGotham/When-in-Rome dataset for some analysis work, but again that's not 100% what you're looking for.
You might like the "iReal Pro" app for the replacement and transposition of jazz standards on your tablet. It's pretty great for that use case versus camera scans.
I had attempted to create a pass for my local library in the past, but never got a working barcode, and this post helped me to understand the issues I was hitting.
I was able to adapt the OP's shell script to generate a working Codabar image (after I figured out that my local library used "A" and "T" as beginning and end markers) that matched the physical card exactly, and there was enough useful metadata for me to piece together a working pass using that barcode as a store card's background image. I ended up using the Pass2U Wallet iOS app directly, rather than hacking around signing keys, but found the documented process helpful.
That's essentially what https://krypt.co/ is...I've used Yubikeys in the past, but have been on Krypton for maybe the past year or so. No problems with it at all, aside from GitHub recently (within the past couple of weeks) not recognizing the authorization despite it working just fine elsewhere. I haven't had a chance to dive deeper into why.
Tiddlywiki is what I use to manage my own personal Zettelkasten as well; it's pretty well suited for the task. There's a bit of ugliness when renaming Tiddlers, but for a lot of inter-related topics, I add an automatically-generated list of backlinks like this: