As my own awareness of some “senior moments” has increased with age, I have looked for and found a method to improving my “filing system”, as you call it.
When younger, we were often able to do any number of very small tasks all day and almost automatically and did not frequently lose things - the “filing system” worked without 100% active conscious effort.
But, not so easily with age.
BUT, I have found that if, in my daily activities, I make an active and deliberate conscious statement to myself (only needs to be in my head, I don’t have to speak it out loud) of what I am doing when I do it (as in: “I’m setting the keys here”), and do so most importantly with the smaller tasks (most inclined to be done automatically too), then I pretty much forget nothing.
My “filing system” works better, when I very actively participate in it. I think this was less essential at a younger age.
I do that (say it out loud) to remember where I parked at the grocery store. As I am walking in, I say, “come out the ‘pharmacy’ door, next row to the right, facing the high school.” Seems to work. But I am young enough I should maybe remember better without that crutch?
One thing at a time. Easy does it. Slow down. Hey! Dear ol' dad was right.
The younger you are, the less you have on your mind. Children are very "in the moment" because it's all new to them. They don't have jobs and bills and relationships and taxes and houses and cars and kids and politics and health issues to distract them from what they happen to be doing. Given the many levels of consciousness we operate on, it's a wonder anyone over 40 can remember anything.