Is it possible to understand what you are lacking functionally through observation of what you struggle with or are worst at?
Of course this presumes the cognitive functions to be a very concrete set of rules and standards, which they aren't.
But here is an example: Im bad at driving, I also dislike it. Some may say that the first exists because of the second. I might agree with that, except the dislike came after the lack of ability.
When driving I tend to drift off and become a danger to those around me. This has resulted in my inability to locate a driving instructor, by dint of scaring off all the ones in the area, and thus ive never learnt to drive.
When I inspected my lack of concentration and ability at driving, I realised there was a connection with my general lack of logistics and planning. Im not a map reader, nor am I one to plan routes.
I also realised that I have no inclination or interest in learning the route specifics of driving; the street names, the locations, the roads with camera's or without.
None of that appeals or interests me and to focus on such information is a stress to my mind. When walking or cycling I know the area by an instinctive nature of familiarity. I can stand in any area of my town and know where the other parts are.
You cannot do this with a car unless you are already well experienced.
In some ways it is self defeating and I ought to push myself to develop whatever it is that I need to perform the act of car driving and logistics.
From this I might discern a lack of Te and possibly even Si. However I could easily be mistaken.
The interesting point here for me is: Am I underdeveloped in these areas because they are strong preferences I have not worked on yet? Or am I underdeveloped in these areas because they belong to a shadow function?
Of course I am open to the fact that this has nothing to do with function theory and specific skillsets can be mastered by anyone.
But that wouldn't explain natural tendencies for certain areas...or lack of tendencies in my case.