Re "...u have to select the share icon to copy files to where you can do what yo..." I am not sure what you mean by a share icon but all I see is shown in the attached screen capture. The DJIFlightRecord_2020........ files are the ones I copied from the computer to the phone, I had no choice over where they 'landed'.
How would I "mail" logs to my self?
Airdrop??????
Re "Does altering the set of flight log files get reflected in the app?" These copied files are unaltered in anyway.
I have played with changing the names of logs being sent to an Android phone and it seems that providing the name is a continuous string of characters the nomenclature is flexible. It does not however like gaps in the name.
With regards to changing the contents of the individual txt's, given they are gibberish to me I wouldn't touch their contents.
If you are asking if the App indicates a increase or decrease in the number of flights as logs are copied to or removed from, the FlightRecord folder, then, under Android, the answer is yes it does, providing it 'likes' the name of those logs.
My first clue that the App does not like gaps in the name came when it would not detect some of my renamed logs, eventually I narrowed the problem down to a dislike of gaps.
With Go and Go4 where there are multiple drones of the same type it can subdivide the flight records into the individual drones but there are no individual totals for the subdivided flights.
The Apps also recognise any given drone by the name under which they first encountered that drone. So if they first met a drone as JoeBloggs_1 the drone will forever be known by the app as JoeBloggs_1 even if the name is subsequently changed.
With regards to an "index file", the only 'unusual' file I occasionally notice is something with something like json somewhere in the name, maybe on the extension.