As root (file manager superuser mode), go to /usr/share/applications, right click on nevernote and choose open with leafpad. Look at the bottom section of the file. You should see a line that looks like this:
Note that Office section is indicated. If your categories line does not show an Office section entry, copy and paste what it says in a reply here.
If that is correct, look for a ShowIn= line. It is usually the bottom line. It may say OnlyShowIn or NotShowIn. If it is NotShowIn, and has LXDE; there, remove the LXDE;, save the change and exit leafpad and file manager superuser mode. If it says OnlyShowIn, add LXDE; save the change and exit leafpad and file manager superuser mode. - Note the semicolon at the end of LXDE. It is necessary.