For the first one (and all 4 of these) every currency has one, I have my speculative guesses as to what it’s potentially used for, but in general I think it makes sense if they have gauge symbols for every currency based on what Apple expects them to be used for:

https://developer.apple.com/design/human-interface-guidelines/gauges

(For myself the “bitcoinsign.gauge.chart.leftthird.topthird.rightthird” symbol feels like a p nice companion for showing something like a mempool.space low/medium/high fee)

Yup, here’s a link to the SF Symbols 6 beta that it’s in https://developer.apple.com/sf-symbols/