Hallo and thank you for the new answers. Yes, I have cut my initial clip into several pieces, deleted some of the resulting clips and moved the remaining ones. At the end I had about ten single clips in one sequence. Now I wanted to change the cropping effect for all clips and found no way to do this. Selecting all the clip by using the Ctrl-Key did not work. Another approch, linking the clips, had no effect on applying the crop effect. Unfortunately saving the settings did not work. (My version is 3.33) Money back is not possible as I have the program for more than 30 days already.
I worked around my problem by removing all effects, saving the clip in low compression and reloading it in a new project where I had only one clip. Unfortunately Videopad seemed to have problems with my lossless codecs (Lagarith and Huffy). (Poor audio quality, crash).