First a disclaimer: my reply will not solve your problem. I had similiar issues with Knotes, between package upgrades always some information stored in the notes was lost -- quite annoying!!!!
I switched to Zim for keeping notes, this is a desktop wiki with a perfectly working GUI interface, but you can also edit the wiki syntax in a text editor like Gedit or Kate. There you can choose where the notes get stored (I think they are plain text files), normally under ~/.zim/YOUR_NOTES_HERE which makes it possible to copy or link it into an OwnCloud- or Dropbox-folder for sharing your notes between different computers.
The config-files are to be found in the directory ~/config/zim/CONFIGURATION_FILES_HERE.
So can even share your custom layouts, keyboard-shortcuts, etc. between your computers.
A lot easier to backup than Knotes where I failed to succeed, some or most of the data gets stored in the Akonadi-database making this a lot trickier.
Je me regarde pour me désoler,
je me compare pour me consoler
Maurice de Talleyrand