Sometimes you learn new tricks by mistake, hitting keys around, or, as in my case, figuring out why this happened all the time and turn the mistake to a tool.
I was sometimes wondering why I got multiple splits when hitting the split function (Command-E) for splitting one single track.
Well, this happens if you have a range in the arrange view selected, if you hit a split, all the tracks in the same range will be split. This could be a nice feature in case you want to copy the same parts to another location. Or, what I did in the example above, I option-dragged the same parts three times to the left, so they were copied over the existing tracks, and the same short section was repeated.
Anyway, the important trick was to make sure that the selection bar, the blue part above, was highlighted by selecting it first.
I don’t know if this is documented, maybe. Anyway, one trick to find undocumented features is to select something, and hit key combinations, and see what happens. Many productivity apps have features that are either not documented, or are not fully enabled yet, but something is there available. Just beware, sometimes undocumented features could also trigger nasty crashes.