Don't work to import a flight log in .csv format from for instance Airdata ... the import in Litchi Mission hub always ends with a "Too Many Waypoints" error.
That's true. However, I have done this manually for reason of exactly reproduce the flight of a lost AC.
Dependent on your requirements (# of flights, comfort,...), you may want to look for scripts to automate the process. Have not tried to find some.
Basic idea and short description:
You need to open the .csv of the respective mission (.csv1 in LitchiApp Folder) with a text editor, open in parallel a (short) mission (.csv2), created in Litchi Mission Hub.
File .csv 2 only serves as reference, and as you compare especially the headlines of the two files, you will notice the difference and what changes need to be done to .csv1 to convert it into a correct mission file.
First change is, to significantly reduce the number of lines to < 100, i.e. by leaving 1 out of 10 lines and removing all others. Then by further comparison, select the columns in .csv 1 to be removed to adapt the format to that of .csv 2.
If the format is correct and lines are within the range of 100, you can copy .csv1 to the LitchApp folder on your SmartPhone and from there upload to the AC.
As already mentioned, this process is highly suitable for automation, but its also no rocket science to try by yourself. Quite interesting to see and understand the FlightRecord Details and composition of a Litchi Mission file.