After uploading more as a million bad pictures with unrecognisable characters from my smartphone, I decided to give my Garmin Virb XE actioncam another trial. It had been resting in the drawer because I have python and xcopy problems and because mly had not come up with an app.
My actioncam makes directories of 150 pictures. So after hours of painstakingly uploading every directory I tried to drag a directory to the mly "Wellcome to the mly uploader " window. That worked, but it made keeping track of the uploaded directories difficult.
Then in the Windows Explorer, I moved two directories to a third directory. I dragged the third directory to the "Wellcome to the mly uploader " window and it uploaded all 318 files.
In the past there was a memory problem and the manual uploader crashed when uploading more as for example 500 pictures. The problem was solved I think, I hope. We will see.