Basically I keep track of my flight plans saving one for each of my flights. I use a naming convention of aaa_bbbb_cccc_dddd where aaa is either VFR or IFR, bbbb is the departure, cccc is the arrival, dddd is other info like runway arrival, sometimes the SU number, or a sequential number to uniquely identify the flight. The files are sorted by date. I can use the Windows search to find flights to or from a specific airport. I usually don’t keep track of flight files but use the same naming if I do. MSFS updates sometimes contain changes that impacted the data in the flight plans or flight files making older ones obsolete.