Of the top of my head, with appropriate probes you could look at voltage and current waveforms to see if there is significant harmonic distortion, and also details about how the distortion is occuring, not just a number in percent. You could see if a transformer is being overdriven and getting into saturation. Also, you could see the actual current waveforms feeding into the rectifier of a VFD and see how well they are matching each other. Mismatched current waveforms could come not only from unequal input voltages, but from a bad rectifier diode, MOV, etc. The effectiveness of a reactor in front of a VFD in reducing harmonic currents could be evaluated, including a reduction in the peaks of this current.
If you can store and print the measured waveforms you might give them to a customer to help show the work that you did, instead of just saying things are OK or not. But I can't say whether or not it will help you make any more money.
When I was using 'scopes and other test equipment it was mostly larger bench models from Tektronix, HP/Agilent/Keysight, Rhode & Schwarz, LeCroy, etc. for developing electronics. Fluke has improved greatly over the years. We used to joke "if it works, it's a fluke". In other words, if you're lucky.