Thank to your quick advice. Now I can make 30 objects at the same time.
By the way, I tired to your two files https://cloud.marum.de/s/nXmbJipEeSqXSBd. Unfortunately "tracking_dock.py" seems not to work well in QGIS 2.18.28
The message is "Python error: Could not load PosiView plugin Error encountered calling classFactory () method See message log (Python error) for details"
However, the old "tracking_dock.py" looks like work. And I will try the new "tracking_dock.py" on QGIS3, too next week.
>I'm curious about the performance of the plugin when dealing with hundreds of objects.
I am going to confirm whether PosiView can make "4770 persons objects" move at this weekend.
I would appreciate if I could get your cooperation on this trial.