As a fellow crewperson on Lifeguard flights, I welcome you to FA. I am not aware of the “L” designation on our flights. As a Lifegaurd flight, even if we are flying to pick up a patient, we can use the “Lifeguard” designator. Since my company uses multi-purpose Learjets (both corporate and medical), I have found the best way to keep track is to input the tail numbers into the “My Flightaware” function of the main site.
That way, all I have to do is click on the “My Flightaware” button, and I find out where all my planes are at the time. Any flight which is Lifeguard shows up in red.
I hope that helps.