It would be nice to have a custom logging feature for variables while printing.
We can call it a blackbox. It can help while dialing in the printer or while debugging. Also it can help to understand the printer and to visualize print parameters.

example variables are: temperature, requested speed, actual speed, requested acceleration...

First step could be a output file after print. It could be a .csv or other text based file -> for manually creating charts with Excel.

Secand step could be a Duet Web live chart.

Example Usage:
-dialing in printer kinematics:
You want to know what are the usual values of speed, accl, while printing.
Are the max. speed, acceleration. values in your config too low or too high.
Are the desired parameters active while printing. (or overwritten from gcode/Slicer)

-Debugging (failed) long prints:
MCU temp., ext. temp., bed. temp., voltage..