[charliehorse]

If you need a fast solution, try to use the spreadsheet feature.
 https://github.com/ddurdle/GDrive-for-KO...D_DB---FAQ

AFAIK this works within the library when you want to resume a movie.    

Yes using the spreadsheet does work from within the library but it doesnt mark tv shows and movies as watched when they have finished which also means the trakt addon doesnt get triggered.    

You're right.
One workaround for this could be, to jump to the end of the movie when you stop watching. Don't press the stop button to "stop" the movie/show, instead use the jump feature or fast foward till the progress bar is at 100% and the movie/show get stopped by kodi and return you to the library screen. Then the movie/show is marked as watched.
It is only meant as a temporary solution. It seems, it doesn't matter what amount of % are entered in the mark as watched field. 

 I have tried letting the movie or show run right to the end
​​​ or jumping to the end it still doesn't get marked as watched when using the spreadsheet but the restore point does work this way.