It's good to see the younger guys thinking outside the box. It has been a long time but years ago, I made a few gadgets pertinent to what I was working on. Otis B base (goolean logic) was a early digital design that revolved around discreet DTL (yes...diode transistor logic). It could be a total beast to troubleshoot. You might have 4 or 5 inputs forming the conditions for as an example perhaps generating a door open pilot. Rather than fight the limitations of a single logic probe, I built a custom unit which had 5 inputs. I used mostly 2N222 transistors and red and green leds for a "high " or "low" state. You could label an entire complex logical circuit and monitor it without the hassle much less danger of shorting out a backplane mishap with a single logic probe. This same circuit also worked well on the Haughton 1092 IC controller. A similar early digital controller that was based off of TTL circuits.

The other circuit was built to help troubleshoot intermittent drive trips on a Sweo DC drive. Since the fault leds didn't latch, often you had no idea of why the drive had tripped. So I built a circuit with 4 window comparators based off LM3302 opamps, a quad Schmidt trigger and D flip flops to latch one of 4 leds. This way you could clearly see which of the fault conditions of the drive had operated prior to being reset by the controller.
Our trade has been full of guys building great custom tools, often mechanical to get things done.