The transfer of a self-created GPX track to my Edge 1030 Plus always fails. I tried it with BaseCamp, Connect and USB cable, the file was always deleted after the restart

you put ir into the New files directory?

There is a limit to the number of Gpx files which can be stored. If the limit is exceeded ( I think 200) then new gps cannot be stored. Then remove older one and try again (when doing manually place the file into New files directory