So, I figured out (by accident) the solution to the problem of Flow not working when I turn on one of my two MacBook Pros or wake them up from sleep mode. If I simply open Logi Options+ on both devices, Flow will recognize the devices and get them talking to each other so that the feature can work seamlessly. I am still "bugged out" 😉 about my MX Anywhere 3 losing the SmartShift or ratchet spin functions when switching between devices (and constantly having to turn them on in settings). However, I'm very grateful that I have a verified fix for Flow.