Where it happens: Ubuntu-Studio 16.04 - XFCE - Thinkstation S20. 
Compliments, this bug-machine is a smart solution. Thanks for that! I found possible duplicates of my problem within a second. Respect.

My problem is the chronology-order of all the notes. Up to a smaller amount of pages, notes keeps the order of tabs, very strictly. But one day, after using it a little luxuriantly, all my pages where mixed up by random. No way, to bring them back in a useful order. My 'in-between'-solution:
When navigation by tabs is getting quite useless anyway, navigate through the window-menu 'Groups' and hope, someone will find a better solution to reorder the mess, one day.