I don’t know how, but I ended up with several pages with the same order index (folder name prefix). manually cleaning that up fixed the order in the panel. as descrbibed in Failing to resort panel page order
the problem that still persists is: whenever I drag an invisible page over to the ‘visible’ column, the page gets inserted at the top (and gets the index 1) – no matter where in the list I drop it.
ok, it looks like this is caused by the fact, that I manually disabled pagination for this view. – is there any way to disable pagination without breaking other things?