These are known as https://en.wikipedia.org/wiki/Parallel_coordinates and are a pretty old technique. Although the wiki lists process control as one of the major users, their history has them as dormant until revived in their modern form in the 1960s, which doesn't quite match your timeline. Perhaps the discrepancy is resolved by whether parallel axes were used as a equation solving aid versus a visualization aid?

They're also not outdated, you can find them in many libraries, like highcharts here: https://www.highcharts.com/docs/chart-and-series-types/paral...

Excellent technical coverage is: Parallel Coordinates for Visualizing Multi-Dimensional Geometry, from 1987 at https://link.springer.com/chapter/10.1007/978-4-431-68057-4_...

Wikipedia links to this 1880 chart: https://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~3...

Don't know if it's what you're referring to, but psychrometric charts are always fun, and any of the thermodynamics charts (Pressure-Enthalpy being an example). The best part? You say the "age of slide rules", but these are still used today.