Thanks for trying to help.
But your addon does not import the notes of the original addon. Besides, it seems not do correct the bugs either.
Here is my solution (for the original addon):

add this Userstyle for all websites, to restore the selectability of note contents:

.__myNoteMainWrapper * {
user-select:text !important;
}
(for example with the stylus addon; you could change it directly in the notes.css of the addon, but I don't know how, it would be great someone would takte this addon in capable hands).

There is no better addon for this task, tried them all.